ACS Research

December 17, 2003

**Comparing Quality Measures:**

**The American Community Survey's Three-year Averages and Census 2000's
Long Form Sample Estimates**

Katie Bench

> Planning, Research,
>
> and Evaluation Division

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height="0.5409722222222222in"}

# CONTENTS

# 

EXECUTIVE SUMMARY v

1\. INTRODUCTION AND BACKGROUND 1

1.1 Census 2000 Long Form 1

1.2 American Community Survey Three-year Averages 3

1.3 Errors in the Data 4

2\. METHODOLOGY 5

2.1 Comparisons of the Quality Measures 5

2.2 Calculation of Standard Errors 7

2.2.1.Standard Errors for Census 2000 Quality Measures 7

2.2.1.1 Design Factors 8

2.2.2 Standard Errors for ACS Quality Measures 9

2.2.3 Standard Errors for the Differences between the ACS and

Census 2000 Quality Measures 10

3\. ANALYSIS/RESULTS 11

3.1 Self-Response Rate 11

> 3.1.1. County Comparisons 12
>
> 3.1.2 Tract Comparisons 14
>
> 3.2 Nonresponse Rates: Sample Units and Occupied Sample Units 16
>
> 3.2.1 County Comparisons 18
>
> 3.2.2 Tract Comparisons 20
>
> 3.3 Item Allocation Rates 22
>
> 3.3.1 County Comparisons 24
>
> 3.3.2 Tract Comparisons 27
>
> 3.4 Sample Completeness Rates 31
>
> 3.4.1 County Comparisons 32

4\. CONCLUSIONS 34

5\. REFERENCES 35

Appendix A: County Level Quality Measures 36

Appendix B: Design Factors Used for Standard Errors of Census Quality
Measures 44

Appendix C: Quality Measures Scatter Plots for Counties 47

Appendix D: Quality Measures Scatter Plots for Tracts 56

**LIST OF TABLES**

Table 1. Number of Counties with Statistically Different Self-response
Rates 13

Table 2. Comparison of Self-response Rates: ACS Three-year Averages and
Census 2000 Long Form Estimates, County Averages 13

Table 3. Number of Tracts with Statistically Different Self-response
Rates, by Tract Group 15

Table 4. Comparison of Self-Response Rates: ACS Three-year Averages and
Census 2000 Long Form Estimates, Tract Group Averages 15

Table 5. Number of Counties with Statistically Different Nonresponse
Rates for Sample Units and Occupied Sample Units 18

Table 6. Comparison of Nonresponse Rates for Sample Units and Occupied
Sample Units: ACS Three-year Averages and Census 2000 Sample Estimates,
County

Averages 18

Table 7. Number of Tracts with Statistically Different Nonresponse Rates
for Sample Units and for Occupied Sample Units, by Tract Group 20

Table 8. Comparison of Nonresponse Rates for Sample Units and Occupied
Sample Units: ACS Three-year Averages and Census 2000 Sample Estimates,
Tract Group Averages 21

Table 9. Number of Counties with Statistically Different Summary Item
Allocation

Rates 25

Table 10. Comparison of Summary Item Allocation Rates: ACS Three-year
Averages and Census 2000 Sample Estimates, County Averages 26

Table 11. Number of Tracts with Statistically Different Summary Item
Allocation Rates, by Tract Group 28

Table 12. Comparison of Summary Item Allocation Rates: ACS Three-year
Averages and Census 2000 Sample Estimates, Tract Group Averages 29

Table 13. Number of Counties with Statistically Different Sample
Completeness

Rates 32

Table 14. Comparison of Sample Completeness Rates: ACS Three-year
Averages and

Census 2000 Sample Estimates, County Averages 33

Table A-1. Comparison of Self-response Rates, Sample Unit Nonresponse
Rates, and Sample Completeness Rates: ACS Three-year Average and Census
2000 Long Form Sample Estimates, by County 36

Table A-2. Comparison of Summary Allocation Rates for Population Items:
ACS Three-year Average and Census 2000 Sample Estimates, by County 38

Table A-3. Comparison of Summary Allocation Rates for Housing Unit
Items: ACS Three-year Average and Census 2000 Sample Estimates, by
County 40

Table A-4. Comparison of Summary Allocation Rates for Population and
Occupied Housing Unit Items: ACS Three-year Average and Census 2000
Sample Estimates, by County 42

Table B-1. Design Factors used to Calculate Standard Errors of Census
2000 Sample Item Allocation Rates 44

**LIST OF FIGURES**

Figure C-1. Self-Response Rates: Scatter Plot of Difference by County 48

Figure C-2. Nonresponse Rates of Sample Units: Scatter Plot of
Difference by

County 49

Figure C-3. Nonresponse Rates of Occupied Sample Units: Scatter Plot of
Difference

by County 50

Figure C-4. Summary Allocation Rates for Population Items: Scatter Plot
of Difference

by County 51

Figure C-5 Summary Allocation Rates for Housing Unit Items: Scatter Plot
of Difference by County 52

Figure C-6. Summary Allocation Rates for Population and Occupied Housing
Unit Items: Scatter Plot of Difference by County 53

Figure C-7. Sample Completeness Rates for Housing Units: Scatter Plot of

Difference by County 54

Figure C-8. Sample Completeness Rates for Household Population: Scatter
Plot of Difference by County 55

Figure D-1. Self-Response Rates: Scatter Plot of Difference by Tract 57

Figure D-2. Nonresponse Rates of Sample Units: Scatter Plot of
Difference by Tract 58

Figure D-3. Nonresponse Rates of Occupied Sample Units: Scatter Plot of
Difference

by Tract 59

Figure D-4. Summary Allocation Rates for Population Items: Scatter Plot
of Difference

by Tract 60

Figure D-5. Summary Allocation Rates for Occupied Housing Unit Items:
Scatter Plot of Difference by Tract 61

Figure D-6 Summary Allocation Rates for Vacant Housing Unit Items:
Scatter Plot of

Difference by Tract 62

Figure D-7. Summary Allocation Rates for Population and Occupied Housing
Unit Items: Scatter Plot of Difference by Tract 63

# EXECUTIVE SUMMARY

The Census Bureau initiated the American Community Survey (ACS)
development program in 1994 to develop and test the feasibility of
producing long form data on a yearly basis, instead of once a decade. In
2001, the Census Bureau initiated the ACS Research and Evaluation
Program to answer questions about the usability and reliability of the
ACS estimates. This report is an evaluation from the Research and
Evaluation Program. The report compares selected quality measures for
the 1999 -- 2001 ACS three-year average estimates to selected quality
measures for the Census 2000 long form estimates.

The ACS data reviewed in this report were collected from 1999 to 2001 in
36 counties across the United States. The 36 counties are not a random
sample of all counties in the United States. Instead these counties were
selected for the ACS demonstration project to represent different types
of areas, containing large cities, medium cities, and rural counties.
While the estimates examined in this report are three-year average
estimates, they are roughly equivalent in terms of their sampling error
to the five-year estimates that the ACS will produce when the survey is
fully implemented. In order to simulate the sampling error for a
five-year average, a greater percentage of the individuals living in
these counties in 1999-2001 were included in each year's sample than
will be included when the ACS moves to full implementation. The quality
measures examined in this report, therefore, may approximate the quality
measures for the five-year averages that can be expected using the
fully-implemented sample size.

We compared the following quality measures:

-   Self-Response Rates

-   Nonresponse Rates for Sample Units

-   Nonresponse Rates for Occupied Sample Units

-   Sample Completeness Rates for Housing Units

-   Sample Completeness Rates for Household Population

-   Item Nonresponse Rates

    The decennial census and the ACS are very different in methodology,
    scope, timing, and visibility. The main emphasis of the decennial
    census is to enumerate the U.S. population and housing; the
    collection of long form data is secondary. The ACS, in contrast, is
    designed to collect long form data only. The difference in the
    purpose of the two operations may be a major reason for the
    statistically significant differences we found between the quality
    measures for the ACS and the Census 2000 long form sample:

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-   The Census 2000 long form estimates exhibited higher self-response
    rates than the ACS estimates, indicating that a greater percentage
    of housing units mailed back the long form census questionnaires
    than mailed back the ACS questionnaires. This finding is reasonable
    considering the high visibility and large advertising campaign of
    Census 2000.

-   The ACS estimates exhibited lower sample unit nonresponse rates,
    lower occupied sample unit nonresponse rates, and lower summary item
    allocation rates (except for vacant housing units) than did the
    Census 2000 sample estimates in majority of the counties and tracts.
    The higher Census 2000 sample nonresponse rates could be a signal of
    somewhat higher nonsampling errors in the census estimates. The
    lower ACS nonresponse rates make sense for several reasons,
    including the ACS's staff of permanent professional interviewers,
    Census 2000's decision not to followup on blank items on mail
    returned questionnaires, and the ACS's smaller and more manageable
    sample size.

-   The ACS estimates exhibited housing unit sample completeness rates
    somewhat closer to one than did the Census 2000 sample estimates.
    However, the household population sample completeness rates for both
    surveys were nearly even. The sample completeness rates measure both
    nonresponse errors and coverage errors and indicate how well the
    target population was represented. A rate of 100 is optimal.

These quality measures suggest that the ACS multi-year averages are at
least as good as the estimates from the long form. When we also consider
the enhanced timeliness of information from the ACS, the superiority of
reengineering the 2010 Census over retaining traditional methods is
clear. In addition, while further study is needed, it appears that the
permanent, on-going nature of the ACS program contributes to lower ACS
nonresponse rates, and hence less chance for nonresponse error and bias
in the estimates.

Number range CHAPTER**1. INTRODUCTION AND BACKGROUND**

To reduce the operational complexity of the decennial census and
increase the currency of detailed population and housing data, the U.S.
Census Bureau has implemented the 2010 Census re-engineering strategy.
The American Community Survey (ACS) is one of three program components
required to achieve the 2010 Census re-engineering strategic goals. The
ACS collects long form data throughout the decade, instead of all at
once in the decennial census.

The proposal to replace the census long form with the ACS has raised
issues concerning the operational feasibility of the ACS, and the
reliability and usability of ACS data. To help answer these questions,
the Census Bureau has conducted and continues to conduct research. In
1994, the Census Bureau began to develop the methods for providing long
form data each year. Two of the programs implemented since then to
develop methods are the Continuous Measurement program and the Census
2000 Supplementary Survey (C2SS). The Continuous Measurement program
began to collect long form data in 1996 in four sites, and has since
expanded to 36 counties. The C2SS was conducted as part of Census 2000
to demonstrate the operational feasibility of collecting long form data
at the national level at the same time as, but independently from Census
2000 (Bureau of the Census, 2001). These and other ACS research programs
have demonstrated the operational feasibility of the ACS, and the
reliability of ACS data. Research objectives have continued more
recently through the implementation of an ACS Research and Evaluation
Program. As part of this research objective, we produced this report to
help data users understand how the quality of the 1999 -- 2001 ACS
three-year average data compares to the Census 2000 long form sample
data. These three years were chosen to center the estimate in the census
year.

This report compares quality measures for the ACS three-year averages
with those for the Census 2000 long form sample for the 36 counties in
the Continuous Measurement Program (see Appendix A) and their associated
tracts (except for the tracts associated with Fort Bend County, Texas
and Harris County, Texas). These counties are not a random sample of
counties in the country, but were chosen to represent different types of
areas: differing county population sizes, different racial or ethnic
groups, highly seasonal populations, migrant workers, American Indian
reservations, improving or worsening economic conditions, and various
predominant occupations or industry types (Bureau of the Census, ACS
Operational Plan, 2003).

Number range CHAPTER

1.  **Census 2000 Long Form**

Census 2000 collected data using two basic types of questionnaires---the
short form, containing only the "100 percent" items asked of the entire
population, and the long form, containing the "100 percent" items as
well as a myriad of detailed housing unit, household, and population
items known as sample items. The "100 percent" items were relationship,
sex, age, Hispanic origin, race, and tenure for occupied housing units,
and vacancy status for vacant housing units. A national average of about
one-in six housing units were expected to be enumerated on the long form
and make up the Census 2000 sample; the other five-sixths of the
addresses were to be enumerated on the short form.

Variable sampling rates were used across the nation to obtain the
national average of the about one-in six housing units expected to be
enumerated on the long form and make up the Census 2000 sample. This was
done to provide relatively more reliable estimates for small areas and
decrease respondent burden in more densely populated areas while
maintaining data reliability. There were four different housing unit
sampling rates, which varied by census block: 1-in-8, 1-in-6, 1-in-4,
and 1-in-2. These rates were assigned based on precensus estimates of
the number of occupied housing units in various geographic and
statistical entities, such as incorporated places and interim census
tracts (Bureau of the Census, Summary File 3 Technical Documentation,
2003).

This comparison project is based on characteristic distributions as
estimated by the Census 2000 sample, and additionally on information
reflecting overall response to the Census 2000 long form questionnaire.
Not all units enumerated on long form questionnaires are eligible to be
members of the Census 2000 sample. To be eligible for inclusion, long
form response records had to meet a set of criteria identifying them as
'sample data defined.' The occupied housing unit or household long form
records had to contain at least one person who was both "100 percent"
data defined and sample data defined. To satisfy these criteria a person
record had to have answers to at least two of the "100 percent"
population items and two of the sample population items. No answers to
any housing items were required of occupied long form units to be
considered census sample-eligible. For vacant long form units to be
placed in the Census 2000 sample they had to have answers to at least
two sample housing items.

In addition to estimates based on housing units and the household
population, the Census 2000 sample also included data from the group
quarters population. These records were removed from the sample for this
analysis. All but one of the Census 2000 quality measures included in
this study are based on information directly affecting the sample. The
one exception is the long form questionnaire self-response rate, which
is based on the count of housing units enumerated using the long form,
and not the count of housing units that are members of the Census 2000
sample (Bench, 2003).

To enumerate the U.S. population, the U.S. Census Bureau distributed and
collected forms using three basic methods: mailout/mailback,
update/leave, and list/enumerate. These are referred to as Type of
Enumeration Areas (TEAs). For mailout/mailback TEAs, questionnaires were
delivered to housing units with city style addresses (house number and
street name) via the U.S. Postal Service. The householder then completed
the questionnaire and returned it via mail. For update/leave TEAs,
enumerators left census questionnaires at housing units for the
householder to complete and mailback. This occurred in areas with
predominantly noncity style addresses. For list/enumerate TEAs,
enumerators visited the housing units, and completed the form while
there. This occurred in remote or sparsely populated areas (Bureau of
the Census, 2000).

In conjunction with the three basic enumeration methods, a variety of
operations were used to collect the "100 percent" and sample items. The
Census 2000 long forms were mailed in March 2000 along with the short
forms; Nonresponse Followup began in late April 2000, and lasted about
nine weeks. During this operation, housing units that had not returned a
form by mail were visited multiple times to secure a response. If no
response could be obtained from the residents, enumerators used a last
resort method known as proxy. In addition, housing units identified as
vacant or nonexistent by the U.S. Postal Service were also visited.
After Nonresponse Followup, the Census Bureau also conducted Coverage
Improvement Followup, and Coverage Edit and Telephone Followup. Coverage
Improvement Followup visited vacant housing units, and newly discovered
addresses. Coverage Edit and Telephone Followup identified and resolved
count discrepancies. Discrepancies occurred if the number of persons
reported for a household did not match the number of persons for whom
census information was provided on the form. The Coverage Edit and
Telephone Followup should not be confused with a content edit to
followup and obtain answers for blank items on a questionnaire. There
was no attempt to followup on items left blank on questionnaires
returned by mail. Blank items on mail returned questionnaires were
statistically inferred (Bureau of the Census, 2001; Bureau of the
Census, 2000).

2.  **American Community Survey Three-year Averages**

The American Community Survey is designed to collect long form data
throughout the decade. This is done with continuous, monthly samples
with three-month collection cycles for each using a combination of
mailout/mailback questionnaires, Computer Assisted Telephone
Interviewing (CATI), and Computer Assisted Personal Interviewing (CAPI).
During the first phase of the three-month collection cycle, the
questionnaires are mailed and a second questionnaire sent to those who
have not responded by mail by a certain date. During phase two of the
cycle, CATI is used to follow-up with housing units not responding by
mail, and for whom telephone numbers have been obtained by vendors.
Finally, during phase three of the cycle, a sub-sample of the
nonresponding housing units is drawn, and CAPI is used to help field
representatives conduct the interviews (Bureau of Census, 2001).

Forms that are returned by mail are processed at the Census Bureau
National Processing Center in Jeffersonville, Indiana. The forms
returned by mail go through a check-in process, are keyed to capture the
data, and then go through Telephone Edit Followup. In Telephone Edit
Followup the keyed response records data undergo a computerized coverage
and content edit. This edit identifies questionnaires where an
insufficient number of questions were answered, or with missing or
inconsistent information on the total count of people. Questionnaires
that fail this edit and for which there is a telephone number are
contacted during Telephone Edit Followup to obtain missing answers
(Bureau of the Census, ACS Operations Plan, 2003).

The ACS samples were selected using variable sampling rates, which
generally paralleled Census 2000. These variable sampling rates provide
relatively more reliable estimates for small areas. For the 1999, 2000,
and 2001 ACS, most of the 36 counties were sampled at an annual rate of
five percent. The exceptions were the larger counties. Specifically, for
Fort Bend and Harris Counties, Texas, the overall housing unit sampling
rate was one percent. For Broward County, Florida; Bronx County, New
York; Lake County, Illinois; San Francisco County, California; and
Franklin County, Ohio, the overall housing unit sampling rate was three
percent. The sampling rate within the county varied by the size of the
governmental unit in which the housing unit was located (Bureau of the
Census, 2003).

Eventhough the ACS sampling rates paralleled the Census 2000 sampling
rates, they were not the same. There were two reasons for this. First,
the ACS used total housing unit counts to determine sampling rates;
Census 2000 used estimates of occupied housing units (which was based on
1990 block vacancy rates) . This was a source for different differential
sampling rates between the ACS and Census 2000 in all 36 counties.
Second, only Census 2000 used minor civil divisions (MCD) to determine
the size of governmental units (in areas with MCDs). This was a source
for different differential sampling rates between the ACS and Census
2000 in areas with MCDs.

The one percent sampling rate in Fort Bend and Harris Counties, Texas
yielded small sample sizes at the tract level. Tract estimates based on
these small sample sizes are not representative of the five-year
averages that will be produced at full ACS implementation levels. The
standard errors based on the one percent sampling rate are much larger
than the five-year average standard errors will be, and therefore, are
not representative of the ACS.

**1.3 Errors in the Data**

The ACS and Census 2000 data used for this comparison are based on
samples, and subject to errors. There are two main types of errors:
sampling error and nonsampling error. Sampling error is the deviation of
a sample estimate from the average of estimates from all possible
samples. The sample estimates may differ from the figures that would be
obtained from interviewing the entire population using the same
questionnaires, instructions, and interviewers. The sample estimates
will also differ from other samples of the population (Bureau of the
Census, Summary File 3 Technical Documentation, 2003).

A measure of sampling error is the standard error. The standard error of
a sample estimate is a measure of the variation among the estimates from
all possible samples. It measures the precision with which an estimate
from a particular sample approximates the average result of all possible
samples (Bureau of the Census, Summary File 3 Technical Documentation,
2003).

Nonsampling error is human and processing error that may be introduced
during any of the various complex operations used to collect and process
data. These errors can be introduced during editing, reviewing, keying,
or interviewing operations, and can include: failing to obtain all
required information from the respondents, obtaining incorrect or
inconsistent information, and recording information incorrectly.
Nonsampling error can affect the data in two ways. First, errors that
are introduced randomly will increase the variability of the data, which
should be reflected in the standard errors. Second, errors that tend to
be consistent in one direction will introduce a bias into the survey
estimates in that direction (Bureau of the Census, Summary File 3
Technical Documentation, 2003).

The quality measures compared in this analysis are computed to help
indicate the presence of potential errors and bias. Nonsampling error
caused by nonresponse is one of the main errors the quality measures
deal with. Nonresponse to particular questions on a questionnaire or
failure to obtain any information for a housing unit allows for the
introduction of bias into the data because the characteristics of the
nonrespondents have not been observed and may differ from those
characteristics reported by respondents. As a result, any imputation
procedure using respondent data may not completely reflect these
differences at either the person or housing unit level or on average
(Bureau of the Census, Summary File 3 Technical Documentation, 2003).

**2. METHODOLOGY**

We computed the quality measures listed below for the 36 counties and
their associated tracts (except for the tracts associated with Fort Bend
County, Texas and Harris County, Texas). Quality measures are indicators
of potential error and bias. We then compared the ACS three-year average
quality measures and the Census 2000 sample quality measures for both
the counties and the tracts. Section 2.1 describes how we compared the
ACS three-year average and Census 2000 sample quality measures. Section
2.2 describes the methods we used to calculate their standard errors.
The quality measures are described in detail in section 3.

-   Self-Response Rate (SRR)

-   Nonresponse Rate for Sample Units (UNR)

-   Nonresponse Rate for Occupied Sample Units (OUNR)

-   Item Allocation Rate

-   Sample Completeness Rate for Housing Units (HCR) (county level only)

-   Sample Completeness Rate for Household Population (PCR) (county
    level only)

    **2.1 Comparisons of the Quality Measures**

    Since the ACS and Census 2000 sample quality measures are both based
    on sample data, we expect them to differ. However, we wanted to know
    if the estimates differ because of sampling error (sampling
    variability) or nonsampling error. To determine this, we calculated
    the difference between the two quality measures, and the standard
    error of this difference. We then used the standard error to
    determine if the difference was due to sampling error or nonsampling
    error. The difference between the quality measures is the ACS
    three-year average estimate minus the Census 2000 sample estimate.

    If the difference is caused by something other than sampling
    variability, we refer to the difference as significant. To determine
    if the difference between the quality measures was significant, we
    calculated a z-score by dividing the difference by its standard
    error. We then determined the probability that the computed z-score
    would yield a value as extreme or more extreme than the value
    computed if the ACS and Census 2000 sample quality measures were
    truly equal. We call this probability the p-value, and compare it
    against some pre-specified level of confidence or alpha value. If
    the p-value is less than the alpha value, the difference is deemed
    to be statistically significant because we are not confident that
    the difference was due to sampling error. If the p-value is greater
    than the alpha value, the difference is deemed not to be
    statistically significant because we are confident that it is due to
    sampling error.

    At the Census Bureau, the standard alpha value for determining
    statistical significance is 0.10. We need to test for statistical
    significance because our estimates are based on samples and not the
    entire population. When we test a tract/county level difference for
    significance using a 0.10 alpha value, the chance of finding that
    difference to be statistically significant would be 0.10. However,
    we tested a large number of tracts/counties, and needed to
    incorporate a multiplicity allowance to allocate the significance
    level equally among all the tracts/counties. To do this, we used the
    Bonferroni multiple comparison procedure to adjust the overall alpha
    value (alpha~N~) to a value (alpha~R~) where the chance of finding
    one or more significant differences by chance alone, among all the
    tracts/counties is 0.10. The Bonferoni multiple comparison procedure
    adjusts alpha~N~ for multiple comparisons by dividing it by the
    number of comparisons (m). So, in the Bonferoni equation
    alpha~R~=alpha~N~/m. For this analysis alpha~N~ is set to 0.10, and
    m is set to the number of counties for the county level quality
    measure comparisons, and the number of tracts for the tract level
    quality measure comparisons.

    For the tract level quality measure comparison, we split the tracts
    into five different groups, and calculated a separate alpha~R~ value
    for each group. So, m is set equal to the number of tracts in the
    tract group. The tract groups are defined based on county and tract
    population sizes. Grouping the tracts according to population size
    helped us see if there were differences in nonresponse and coverage
    between tracts of different population size, and made it easier to
    graphically display significant tract differences. In addition, we
    excluded tracts with a population less than 500 from the analysis
    because the estimates would be based on a small amount of data. The
    five tract groups are defined as follows.

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-   Group 1 - tracts in small counties (under 100,000 persons) and tract
    population greater than 500 (207 tracts)

-   Group 2 - tracts in medium counties (100,000 - 1,000,000 persons)
    and tract population between 500 and 4000 (592 tracts)

-   Group 3 - tracts in medium counties (100,000 - 1,000,000 persons)
    and tract population greater than 4000 (580 tracts)

-   Group 4 - tracts in large counties (1,000,000+ persons) and tract
    population between 500 and 4000 (401 tracts)

-   Group 5 - tracts in large counties (1,000,000+ persons) and tract
    population greater than 4000 (470 tracts)

In addition to testing the difference between the ACS three-year average
and Census 2000 sample quality measure for each county/tract for
significance, we also tested the difference between the average quality
measures for significance. That is, we tested the difference between the
average of the county/tract ACS three-year average quality measures and
the average of the county/tract Census 2000 sample quality measures. We
tested the difference between the average quality measures using the
margin of error. The margin of error is used to calculate a confidence
interval for an estimate. A confidence interval is defined as a range
about a given estimator that has a specified probability of containing
the results of a complete interview. The margin of error specifies the
range of the confidence interval about a given estimator. In other
words, the confidence interval is equal to the estimator plus or minus
the margin of error. The margin of error is calculated by multiplying
the standard error of the difference by the critical z-score value. The
critical z-score is the z-score yielded when the resulting p-value is
equal to the alpha value. Any z-scores equal to or greater than the
critical z-score value are deemed significant. For this comparison, we
used an alpha value of 0.10. The critical z-score for alpha~N~, 0.10 is
1.645. So, the margin of errors shown in the tables of this report are
equal to 1.645 times the standard error of the difference. Note, since
we were only testing the one difference, we did not adjust for
multiplicity. Once the margin of error is determined, a confidence
interval can be computed. The upper limit of the confidence interval is
the difference plus the margin of error. The lower limit of the
confidence interval is the difference minus the margin of error. If this
interval contains zero, the difference is not significantly different.
So, if the margin of error is greater than the absolute value of the
difference, the confidence interval will contain zero and the difference
will not be significant. If the margin of error is not greater than the
absolute value of the difference, the confidence interval will not
contain zero, and the difference will be significant.

Note, even though a difference is statistically significant, the
difference may be very small. The small difference may be statistically
significant as a result of a large sample size and small standard error.
So, a very small difference with a small standard error estimated from a
large sample size may be statistically significant even though the
difference is of no practical importance.

**2.2 Calculation of Standard Errors**

The calculation of the standard errors for the Census 2000 sample and
ACS three-year averages quality measures are described in this section.
Section 2.2.1 describes the calculation of the standard errors of the
Census 2000 sample quality measures. They were computed using the Census
2000 published design factors. Section 2.2.2 describes the calculation
of the standard errors of the ACS three-year average quality measures.
Section 2.2.3 describes the calculation of the standard error of the
difference between the ACS three-year average and Census 2000 sample
quality measures. For the ACS, the single year estimates were obtained
directly via a replication method, and then used to calculate the ACS
three-year average standard errors.

*2.2.1 Standard Errors for Census 2000 Quality Measures*

To estimate standard errors for the Census 2000 quality measures, we
applied Census 2000 long form data variance estimation procedures. The
standard errors for the Census 2000 self-response rates, sample unit
nonresponse rates, and item allocation rates were calculated as
described below.

![](media/image2.wmf)

Number range CHAPTERwhere, B is the base of the percentage or
denominator of the rates shown in sections 3.1 through 3.4, and DF is
the design factor defined in section 2.2.1.1. For these standard errors,
if p was less than 2 percent or greater than 98 percent, then p was set
to 2 percent. Also, we set any of the standard errors greater than 70 to
70.

The standard errors for the Census 2000 sample completeness rates were
calculated as described below.

![](media/image3.wmf)sample completeness rate

![](media/image4.wmf)

where ![](media/image5.wmf) is an actual Census 2000 count based on the
"100 percent" items, and therefore has no standard error.
![](media/image6.wmf) is the Census 2000 total housing units for the
housing unit sample completeness rate, and the Census 2000 total
household population for the household population sample completeness
rate. Therefore, ![](media/image7.wmf)was treated as a constant in the
sample completeness rate standard errors.

![](media/image8.wmf)

Number range CHAPTERwhere N is the size of the publication area or in
this case ![](media/image9.wmf), and DF is the design factor.

It should be noted that the formulae
for![](media/image10.wmf)and![](media/image11.wmf)are derived from the
simple random sample variance for a total with a 1-in-6 sampling rate.
In addition, the method used to calculate ![](media/image12.wmf)
underestimates (overestimates) the standard error if the two items in
the rate are negatively (positively) correlated. For more information on
the Census 2000 long form variance procedures, see the Summary File 3
Technical Documentation, released in 2003. This can be found on the U.S.
Census Bureau web site at http://www.census.gov/prod/cen2000/doc/sf3.pdf
.

*2.2.1.1 Design Factors*

The design factor used in the Census 2000 long form variance procedure
is the ratio of the estimated standard error to the standard error of a
simple random sample. This reflects the effects of the actual sample
design and the complex ratio estimation procedure used for Census 2000
(Summary File 3 Technical Documentation, 2003). There are published
Census 2000 design factors for a wide range of housing unit and
population characteristics (Asiala and Haines, 2002). These design
factors are available for each state and the United States, and are
calculated by the Number range CHAPTERfour levels of percent in sample
(observed sampling rate). The characteristics for which design factors
are published can be found in the Summary File 3 Technical
Documentation. The four levels of percent in sample are:

-   Level 1 - less than 15 percent

-   Level 2 - 15 percent to less than 25 percent

-   Level 3 - 25 percent to less than 35 percent

-   Level 4 - 35 percent or more

    To calculate the standard errors for the Census 2000 long form
    quality measures, we first identified the appropriate design factors
    to use in the equation. The first step was to identify the
    appropriate percent-in-sample level for each of the 36 counties and
    tracts. The percent in sample for varying geographic levels is
    available on the Census Bureau web site.

    The second step was to select the design factor of the most related
    housing or population characteristics. There are not directly
    corresponding published designed factors for all of the quality
    measures. So, we determined the design factor to use in the standard
    error calculation by:

```{=html}
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```
-   Identifying housing unit/population characteristic with published
    design factors that correlate to the quality measure.

-   Identifying the correlated housing unit/population characteristic
    with the largest published design factor for each state, and
    applying this design factor to the quality measure values for the
    counties and tracts that lie within a state. Using the largest
    published design factor provided a conservative standard error
    estimate.

Appendix B contains a list of the quality measures and the housing or
population characteristic group design factor used to calculate standard
errors for the quality measures. The national and state design factors
can be found in chapter 8 of the Summary File 3 Technical Documentation.

*Number range CHAPTERNumber range CHAPTER2.2.2 Standard Errors for ACS
Quality Measures*

For the ACS quality measures, the single year quality measures and
standard errors were computed first. That is, the 1999, 2000, and 2001
quality measures with their associated standard errors were computed
separately first. Then they were combined to produce the three-year
average quality measure and standard error. The standard errors for the
single year quality measures were obtained directly via a replication
method. The standard errors (SE) for the three-year average quality
measures were then computed as follows (Bench, 2003).

Let ![](media/image13.wmf) , where N stands for numerator and D stands
for denominator.

Year = 1999, 2000, or 2001

![](media/image14.wmf) and ![](media/image15.wmf)

![](media/image16.wmf), ![](media/image17.wmf)

![](media/image18.wmf)

![](media/image19.wmf)

![](media/image20.wmf)

If the standard error of N~Year~ or D~Year~ was calculated as zero using
the replication method, we used the approximation below to obtain their
standard errors. This would happen if N~Year~=0 or D~Year~=0, and
sometimes for nonzero estimates.

![](media/image21.wmf)

Number range CHAPTERwhere the average weight is the maximum of the
average person and average household final weights for observations in
the county for that year.

When any of the single year estimates have been approximated this way,
the standard error of the three-year average rate can be quite large.

If the value calculated for SE(Rate~3yr~) was greater than 70, the
standard error of the three-year average rate was set to 70.

If D~3yr~ = 0, meaning there were no observations in the denominator for
any of the three years, the standard error for the three year average
rate was set to missing.

3.  *Standard Errors for the Differences between the ACS and Census 2000
    Quality Measures*

The standard errors for the differences between the ACS and census
quality measures were calculated as follows.

![](media/image22.wmf)

where difference = Rate~ACS3yr~ - Rate~Census~

It should be noted that the standard error of the difference does not
take into account the covariance between the ACS quality measure and the
census quality measure. So, this method overestimates the standard error
of the difference.

**3. ANALYSIS/RESULTS**

A description of each quality measure and summary of the ACS three-year
average and Census 2000 quality measure comparison results is given in
this section. Section 3.1 covers the self-response rate. Section 3.2
covers the sample unit nonresponse rate and the occupied sample unit
nonresponse rate. Section 3.3 covers the item allocation rates, and
section 3.4 covers the sample completeness rates.

**3.1 Self-Response Rate**

To help measure the public cooperation with the ACS and Census 2000 long
form, we calculated the self-response rate. The self-response rate
measures the percent of occupied housing units that mailed back their
questionnaire. One minus the self-response rate (1 -- self-reponse rate)
shows the percent of data that need collecting in follow-up operations.
These followup operations can have an important effect on the quality of
the data and cost of the survey. Self-response rates were calculated for
each of the 36 ACS counties, and for tracts in 34 ACS counties. (The
tracts in Fort Bend County, Texas and Harris County, Texas were
excluded.[^1]). The county-level comparison results are presented in
section 3.1.1, and the tract-level comparison results are presented in
section 3.1.2.

The Census 2000 long form self-response rate is the percent of all
occupied housing units enumerated in mailback TEAs[^2] on long form
questionnaires that were returned by mail. The numerator and denominator
of the percent are weighted by the reciprocal of the sampling fraction
used to designate long form sample units for the block in which they
were enumerated. This weight is equal to 2, 4, 6 or 8. The weighted
block level long form units are aggregated to the county/tract level,
and the rate computed from the weighted county/tract counts. Note, the
numerator and denominator of this rate also include noninterviews. The
noninterviews are housing units that mailed back a questionnaire *but*
did not provide enough information to be considered 'sample data
defined.' So, these housing units were not eligible for inclusion in the
Census 2000 sample.

The ACS three-year average self-response rate is the percent of all
occupied housing units that mailed back a questionnaire. The numerator
and denominator of this percent are weighted by their probability of
selection or the initial ACS sampling weight multiplied by the CAPI
subsampling weights (base weights). The numerator includes the base
weighted self-response noninterviewed units and the denominator includes
all base weighted noninterviewed units.

The self-response rate formulae are below.

-   Census 2000 long form self-response rate = (weighted count of
    occupied self-response long form housing units enumerated in
    mailback TEAs / weighted count of occupied long form housing units
    enumerated in mailback TEAs) × 100

-   ACS self-response rate = (weighted count of occupied self-response
    housing units including self-response noninterviews / weighted count
    of total occupied housing units including noninterviews) × 100

*Number range CHAPTER3.1.1 County Comparisons*

This section contains the county level quality measures comparison
results. In this section we compare the ACS three-year average and
Census 2000 long form self-response rate differences for each of 35
counties, and then examine the differences when the values are averaged
across all the counties. Vilas County, Wisconsin was excluded from the
self-response rate comparison. For this county, there is no Census 2000
long form self-response rate because the county was not part of a
mailback TEA. The entire county was part of a list/enumerate TEA, so the
denominator or universe of the self-response rate is zero.

Table 1 shows the number of counties with statistically significantly
different ACS three-year average and Census 2000 long form self-response
rates. More specifically, it shows three numbers. First, it shows the
number of counties whose self-response rates were not statistically
significantly different. Second, it shows the number of counties whose
self-response rates were statistically significantly different with the
self-response rates for the ACS three-year averages being larger than
the Census 2000 long form estimates. Third, it shows the number of
counties whose self-response rates were statistically significantly
different with the self-response rate for the Census 2000 long form
being larger than the ACS three-year estimate. To determine the number
of counties with statistically significantly different self-response
rates, we calculated a z-score for each county. We then compared the
z-score against the alpha value yielded by the Bonferoni multiple
comparison procedure (see section 2) to see which of the counties were
statistically significantly different.

While Table 1 shows the results of comparing each of the county
differences, Table 2 shows the results of comparing the average of the
35 county self-response rates. The second column in Table 2 shows the
average of the 35 county ACS three-year average self-response rates. The
third column shows the average of the 35 county Census 2000 long form
self-response rates. Column four shows the differences between the ACS
and census average self-response rates, where the difference is the ACS
average minus the census average. Column five contains the margin of
error for the difference of the average.

  ---------------------------------------------------------------------------------
  **Table 1. Number of Counties                                     
  with Statistically Significantly                                  
  Different Self-response Rates                                     
  ^C^**                                                             
  --------------------------------- --------------- --------------- ---------------
  **Quality Measure**               **Number of 35  **Number of 35  **Number of 35
                                    Counties Not    Counties        Counties
                                    Statistically   Statistically   Statistically
                                    Significantly   Significantly   Significantly
                                    Different**     Different with  Different with
                                                    ACS \> Census** Census \> ACS**

  Self-response rate                3               0               32

  C -- Comparisons are based on a                                   
  non-random sample of counties                                     
  ---------------------------------------------------------------------------------

+----------------------------------+-------+-------+---------+--------+
| **Table 2. Comparison of         |       |       |         |        |
| Self-response Rates: ACS         |       |       |         |        |
| Three-year Averages and Census   |       |       |         |        |
| 2000 Long Form Estimates, County |       |       |         |        |
| Averages**                       |       |       |         |        |
+==================================+=======+=======+=========+========+
| **Quality Measure**              | **ACS | **C   | *       | **     |
|                                  | Aver  | ensus | *Differ | Margin |
|                                  | age** | Aver  | ence^D^ | of     |
|                                  |       | age** | of      | Erro   |
|                                  |       |       | Ave     | r^C^** |
|                                  |       |       | rages** |        |
+----------------------------------+-------+-------+---------+--------+
| Self-response rate               | 55.3% | 68.1% | -12.8%  | ± 3.6% |
+----------------------------------+-------+-------+---------+--------+
| D -- The difference is the ACS   |       |       |         |        |
| average minus the Census 2000    |       |       |         |        |
| average.                         |       |       |         |        |
|                                  |       |       |         |        |
| C -- This comparison is based on |       |       |         |        |
| a non-random sample of counties  |       |       |         |        |
+----------------------------------+-------+-------+---------+--------+

Table 1 and Table 2 show that the census usually collected more forms by
self-response than the ACS. Table 1 shows that 32 out of the 35 counties
were statistically significantly different. For all 32 counties with
statistically significantly different self-response rates, the
self-response rate for the Census 2000 long form was larger than the ACS
three-year average estimate. Table A-1 in Appendix A contains the ACS
three-year average and Census 2000 long form self-response rates (SRR)
for each of the 36 counties. The three counties whose differences are
not statistically significant are marked with an "NS" in the table.
Table 2 shows, that on average the self-response rate for the Census
2000 long form was 12.8 percent larger than the ACS three-year average
estimate. Since the margin of error for the difference is only 3.6
percent, the resulting confidence interval would not contain zero. So,
the average difference is statistically significant.

Figure C-1 in Appendix C displays the county-level self-response rate
differences for the 35 counties through the use of a one-dimensional
scatter plot. For this plot, differences between the ACS three-year
averages and the Census 2000 sample quality measures are located on the
vertical axis; counties are on the horizontal axis. We sorted counties
by their 100 percent count of census housing units. The sort was in
ascending order, from left to right. For example, the difference for the
county with the smallest count is the left-most point in Figure C-1,
while the difference for the county with the largest count is the
right-most point. We used a "jittering" process so that we could plot
the differences in this way. The "jittering" process assigned a unique
integer to each county so as to achieve this sort, where the county with
the smallest count received the smallest integer, etc.

Figure C-1 shows that the self-response rate for the ACS three-year
average was consistently lower than the Census 2000 long form estimate.
These differences are usually centered on --10. It also shows that the
counties with the smaller number of census housing units tend to have
the largest differences. Statistically significant differences are
indicated by an "X" on this plot.

The results presented in Table 1, Table 2, Appendix A, and Figure C-1,
show that in general, the census collected more forms via self-response
than the ACS. The higher census long form self-response rates mean that
the success of the census depended less on followup operations than did
the success of the ACS. The higher census long form self-response rates
are to be expected considering the high visibility and large advertising
campaign of Census 2000.

*Number range CHAPTER3.1.2 Tract Comparisons*

This section contains the self-response rate comparison for the tracts.
In this section we compared the ACS three-year average and Census 2000
long form self-response rate differences for the tracts in the 34
counties by tract group, and then compared the differences when the
values were averaged across all the counties by tract group.

Table 3 shows the number of tracts with statistically significantly
different ACS three-year average and Census 2000 long form self-response
rates for each of the five tract groups. More specifically, it shows
three numbers. First, it shows the number of tracts for each group whose
self-response rates were not statistically significantly different.
Second, it shows the number of tracts for each group whose self-response
rates were statistically significantly different with the self-response
rate for the ACS three-year average being larger than the Census 2000
long form estimate. Third, it shows the number of tracts for each group
whose self-response rates were statistically significantly different
with the self-response rate for the Census 2000 long form being larger
than the ACS three-year average estimate. To determine the number of
tracts with statistically significantly different self-response rates,
we calculated a z-score for each tract. We then compared the z-score
against the alpha value yielded by the Bonferoni multiple comparison
procedure (see section 2) to see which of the tracts were statistically
significantly different. We used the Bonferoni multiple comparison
procedure to obtain a different alpha value for each tract group.

While Table 3 shows the results of comparing each tract difference,
Table 4 shows the results of comparing the average of the tract
self-response rates for each group. The third column in Table 4 shows
the average of the ACS three-year average tract self-response rates. The
fourth column shows the average of the Census 2000 long form tract
self-response rates. Column five shows the differences between the ACS
and census average self-response rates, where the difference is the ACS
average minus the census average. Column six contains the margin of
error for the difference of the average.

+-------------------------+------+---------+-----------+-------------+
| **Table 3. Number of    |      |         |           |             |
| the Tracts with         |      |         |           |             |
| Statistically           |      |         |           |             |
| Significantly Different |      |         |           |             |
| Self-response Rates, by |      |         |           |             |
| Tract Group ^C^**       |      |         |           |             |
+=========================+======+=========+===========+=============+
| **Quality Measure**     | **T  | *       | **Number  | **Number of |
|                         | ract | *Number | of Tracts | Tracts      |
|                         | Gr   | of      | Stat      | St          |
|                         | oup^ | Tracts  | istically | atistically |
|                         | N^** | Not     | Sign      | Si          |
|                         |      | Statis  | ificantly | gnificantly |
|                         |      | tically | Different | Different   |
|                         |      | Signif  | with ACS  | with Census |
|                         |      | icantly | \>        | \> ACS**    |
|                         |      | Diff    | Census**  |             |
|                         |      | erent** |           |             |
+-------------------------+------+---------+-----------+-------------+
| Self-response rate      | 1    | 149     | 0         | 42          |
+-------------------------+------+---------+-----------+-------------+
|                         | 2    | 578     | 0         | 11          |
+-------------------------+------+---------+-----------+-------------+
|                         | 3    | 556     | 0         | 23          |
+-------------------------+------+---------+-----------+-------------+
|                         | 4    | 387     | 0         | 14          |
+-------------------------+------+---------+-----------+-------------+
|                         | 5    | 396     | 8         | 66          |
+-------------------------+------+---------+-----------+-------------+
| N -- Note, group 1      |      |         |           |             |
| contains 191 tracts,    |      |         |           |             |
| group 2 contains 589    |      |         |           |             |
| tracts, group 3         |      |         |           |             |
| contains 579 tracts,    |      |         |           |             |
| group 4 contains 401    |      |         |           |             |
| tracts, and group 5     |      |         |           |             |
| contains 470 tracts.    |      |         |           |             |
|                         |      |         |           |             |
| C -- Comparisons are    |      |         |           |             |
| based on a non-random   |      |         |           |             |
| sample of counties      |      |         |           |             |
+-------------------------+------+---------+-----------+-------------+

+-----------------------+------+------+------+----------+----------+---+
| **Table 4. Comparison |      |      |      |          |          |   |
| of Self-response      |      |      |      |          |          |   |
| Rates: ACS Three-year |      |      |      |          |          |   |
| Averages and Census   |      |      |      |          |          |   |
| 2000 Long Form        |      |      |      |          |          |   |
| Estimates, Tract      |      |      |      |          |          |   |
| Group Averages**      |      |      |      |          |          |   |
+=======================+======+======+======+==========+==========+===+
| **Quality Measure**   | **T  | *    | **Ce | **Diffe  | **Margin |   |
|                       | ract | *ACS | nsus | rence^D^ | of       |   |
|                       | Gr   | A    | A    | of       | Er       |   |
|                       | oup^ | vera | vera | Av       | ror^C^** |   |
|                       | N^** | ge** | ge** | erages** |          |   |
+-----------------------+------+------+------+----------+----------+---+
| Self-response rate    | 1    | 5    | 6    | -12.8%   | ± 2.0%   |   |
|                       |      | 4.8% | 7.6% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 2    | 6    | 6    | -6.7%    | ± 1.2%   |   |
|                       |      | 2.8% | 9.5% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 3    | 6    | 6    | -8.0%    | ± 1.1%   |   |
|                       |      | 0.3% | 8.4% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 4    | 4    | 5    | -9.3%    | ± 1.8%   |   |
|                       |      | 8.3% | 7.6% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 5    | 5    | 6    | -9.2%    | ± 1.5%   |   |
|                       |      | 1.5% | 0.7% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
| N -- Note, group 1    |      |      |      |          |          |   |
| contains 191 tracts,  |      |      |      |          |          |   |
| group 2 contains 589  |      |      |      |          |          |   |
| tracts, group 3       |      |      |      |          |          |   |
| contains 579 tracts,  |      |      |      |          |          |   |
| group 4 contains 401  |      |      |      |          |          |   |
| tracts, and group 5   |      |      |      |          |          |   |
| contains 470 tracts.  |      |      |      |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
| D -- The difference   |      |      |      |          |          |   |
| is the ACS average    |      |      |      |          |          |   |
| minus the Census 2000 |      |      |      |          |          |   |
| average.              |      |      |      |          |          |   |
|                       |      |      |      |          |          |   |
| C -- This comparison  |      |      |      |          |          |   |
| is based on a         |      |      |      |          |          |   |
| non-random sample of  |      |      |      |          |          |   |
| counties              |      |      |      |          |          |   |
+-----------------------+------+------+------+----------+----------+---+

Some tracts were excluded from the self-response rate comparison. For
these tracts, there is no Census 2000 long form self-response rate
because the entire tract was part of the list/enumerate TEA. So, the
denominator or universe of the self-response rate is zero. So, for group
1, 16 tracts were removed from the self-response rate comparison. For
group 2, three tracts were removed, and for group 3, one tract was
removed. There are now 191 tracts, 589 tracts, and 579 tracts in groups
1, 2, and 3 respectively for the self-response rate comparisons.

Table 3 shows that the only two groups to yield more than 10 percent of
their tract differences statistically significant are group 1 and group
5. For group 1, 22.0 percent (42 out of 191) of the tract differences
are statistically significant. For group 2, 1.9 percent (11 out of 589)
of the tract differences are statistically significant. For group 3, 4.0
percent (23 out of 579) of the tract differences are statistically
significant. For group 4, 3.5 percent (14 out of 401) of the tract
differences are statistically significant. For group 5, 15.7 percent (74
out of 470) of the tract differences are statistically significant. So,
we see the largest number of statistically significant differences for
the tracts in small counties (group 1), and the tracts with large
populations in counties with large populations (group 5). In addition,
for all of the statistically significant differences for groups 1, 2, 3,
or 4, the Census 2000 long form self-response rates were larger than the
ACS three-year average rates. For group 5, for 66 out of the 74
statistically significant differences, the ensus self-response rate was
larger than the ACS self-response rate. So, for groups 1 and 5, the
census received a larger number of forms via self-response.

Table 4 shows that for all five groups the census on average, received a
larger number of forms via self-response. The average tract census
self-response rate for all five groups is larger than the average tract
ACS self-response rate. The margin of error for each of the five groups
was less than the absolute value of the difference between the averages.
So, the difference between the average is statistically significantly
different for all five groups.

Figure D-1 in Appendix D displays tract-level self-response rate
differences through the use of a one-dimensional scatter plot. We
grouped all of the tract-level differences by tract group. For this
plot, differences between the ACS three-year average and Census 2000
long form self-response rate are located on the vertical axis; tracts
and tract groups are on the horizontal axis. We sorted tracts within
each tract group by their 100 percent count of census housing units. The
sorts were in ascending order, from left to right, within each tract
group. For example, the difference for the tract with the smallest count
is the left-most point within each tract group, while the difference for
the tract with the largest count is the right-most point within each
tract group. We used a "jittering" process so that we could plot the
differences in this way. Within each tract group, the "jittering"
process assigned a unique integer to each tract so as to achieve this
sort, where the tract with the smallest count received the smallest
integer, etc.

Figure D-1 shows that for each tract group, a majority of the ACS
three-year average self-response rates are lower than the Census 2000
long form self-response rates. The majority of the differences are
between --20 and 10. Statistically significant differences are indicated
by an "X" on these plots.

The results presented in Table 3, Table 4, and Figure D-1, echo the
county level results showing that on average, the census received a
larger number of forms via self-response than the ACS.

**3.2 Nonresponse Rates: Sample Units and Occupied Sample Units**

We calculated the sample unit nonresponse and occupied sample unit
nonresponse rates as measures of the overall success of the ACS and
Census 2000 data collection and to indicate potential nonsampling errors
in the final estimates. These rates were calculated for each of the 36
ACS counties, and for tracts in the 34 ACS tract-level comparison
counties. The county-level comparison results are presented in section
3.2.1, and the tract-level comparison results are presented in section
3.2.2.

Sample unit nonresponse rates measure the percent of housing units for
which we did not obtain enough information for the units to be
considered interviews (see below) . Such nonresponse can introduce bias
into the sample estimates because the characteristics of noninterviewed
units and their residents may differ from the characteristics of
interviewed units and their residents. While the ACS and census used
similar, but not identical, rules to determine which housing units
provided enough information to be considered interviews, they treated
noninterviews differently during weighting and estimation. The ACS
accounts for noninterviewed units by applying noninterview factors. The
census did not use any noninterview adjustment.

The numerator of the Census 2000 sample unit nonresponse rate is the
Census 2000 total housing units minus the Census 2000 weighted count of
long form sample data defined housing units. The denominator is the
Census 2000 total housing units. Each long form sample data defined
housing unit is weighted by the reciprocal of the sampling fraction used
to designate long form sample units for the block in which it was
enumerated. This weight is equal to 2, 4, 6 or 8.

The numerator of the census formula represents the shortage in the
Census 2000 sample of housing units due to response records for long
form units not being "sample data defined." It is expressed as a percent
of the total enumerated units. To be sample data defined (SDD), an
occupied census long form unit had to contain at least one person who
was both "100 percent" data defined and sample data defined. To satisfy
these criteria a person record had to have answers to at least two of
the "100 percent" population items and two of the sample population
items. Housing item responses were not required of occupied long form
units in order to be placed in the Census 2000 sample. Vacant long form
units had to have answers to at least two sample housing items to be
placed in the Census 2000 sample.

The numerator of the ACS three-year average sample unit nonresponse rate
is the base weighted count of noninterviewed units, and the denominator
is the base weighted count of total (noninterviewed plus interviewed)
housing units.

The ACS uses an "Acceptability Index" (AI) to determine whether a unit
provided enough data to be considered successfully interviewed. The AI
index is computed by adding the number of basic items with answers
(e.g., age, complete date of birth, race, etc.), and then dividing this
sum by the number of household members. Households with AIs of less that
2.5 are treated as survey noninterviews. Vacant housing units are not
subjected to this AI requirement, but are included in the denominator of
the ACS total sample unit nonresponse rate.

The sample unit nonresponse rate formulae are below.

The Census 2000 sample unit nonresponse rates are:

-   Total sample unit nonresponse rate = \[(Census 2000 total housing
    units -- Census 2000 weighted count of long form sample data defined
    housing units) / Census 2000 total housing units\] × 100

-   Occupied sample unit nonresponse rate = \[(Census 2000 occupied
    housing units -- Census 2000 weighted count of long form occupied
    sample data defined housing units) / Census 2000 occupied housing
    units\] × 100

The ACS sample unit nonresponse rates are:

-   Total sample unit nonresponse rate = (weighted count of
    noninterviewed units / weighted count of total (noninterviewed plus
    interviewed) housing units) × 100

-   Occupied sample unit nonresponse rate = (weighted count of
    noninterviewed units / weighted count of total occupied housing
    units) × 100

*Number range CHAPTER3.2.1 County Comparisons*

This section contains the nonresponse rate comparisons for sample units
and occupied sample units for counties. In this section we compare the
ACS three-year average and Census 2000 sample unit nonresponse rate
differences for each of the 36 counties, and then compare the
differences when the values were averaged across all the counties.

Table 5 shows the number of counties with statistically significantly
different ACS three-year average and Census 2000 sample unit nonresponse
rates and occupied sample unit nonresponse rates. Table 6 shows the
results of comparing the average of the 36 county rates.

  ---------------------------------------------------------------------------------
  **Table 5. Number of Counties                                     
  with Statistically Significantly                                  
  Different Nonresponse Rates for                                   
  Sample Units and Occupied Sample                                  
  Units ^C^**                                                       
  --------------------------------- --------------- --------------- ---------------
  **Quality Measure**               **Number of 36  **Number of 36  **Number of 36
                                    Counties Not    Counties        Counties
                                    Statistically   Statistically   Statistically
                                    Significantly   Significantly   Significantly
                                    Different**     Different with  Different with
                                                    ACS \> Census** Census \> ACS**

  Sample unit nonresponse rate      9               1               26

  Occupied sample unit nonresponse  13              1               22
  rate                                                              

  C -- Comparisons are based on a                                   
  non-random sample of counties                                     
  ---------------------------------------------------------------------------------

+----------------------------------+-------+-------+---------+--------+
| **Table 6. Comparison of         |       |       |         |        |
| Nonresponse Rates for Sample     |       |       |         |        |
| Units and Occupied Sample Units: |       |       |         |        |
| ACS Three-year Averages and      |       |       |         |        |
| Census 2000 Sample Estimates,    |       |       |         |        |
| County Averages**                |       |       |         |        |
+==================================+=======+=======+=========+========+
| **Quality Measure**              | **ACS | **C   | *       | **     |
|                                  | Aver  | ensus | *Differ | Margin |
|                                  | age** | Aver  | ence^D^ | of     |
|                                  |       | age** | of      | Erro   |
|                                  |       |       | Ave     | r^C^** |
|                                  |       |       | rages** |        |
+----------------------------------+-------+-------+---------+--------+
| Sample unit nonresponse rate     | 4.4%  | 9.7%  | -5.3%   | ± 1.5% |
+----------------------------------+-------+-------+---------+--------+
| Occupied sample unit nonresponse | 5.2%  | 8.7%  | -3.5%   | ± 1.3% |
| rate                             |       |       |         |        |
+----------------------------------+-------+-------+---------+--------+
| D -- The difference is the ACS   |       |       |         |        |
| average minus the Census 2000    |       |       |         |        |
| average.                         |       |       |         |        |
|                                  |       |       |         |        |
| C -- This comparison is based on |       |       |         |        |
| a non-random sample of counties  |       |       |         |        |
+----------------------------------+-------+-------+---------+--------+

Table 5 and Table 6 show that the ACS usually had less unit nonresponse
than the Census 2000 sample. The lower sample unit nonresponse rates for
the ACS suggest that the ACS collected more information during follow-up
operations than the census. Table 5 shows that 27 out of the 36 counties
had statistically significantly different sample unit nonresponse rates,
and 23 out of 36 had statistically significantly different occupied
sample unit nonresponse rates. For 26 counties with statistically
significantly different sample unit nonresponse rates, the sample unit
nonresponse rate for the Census 2000 sample was larger than the ACS
three-year average estimate. For 22 counties with statistically
significantly different occupied sample unit nonresponse rates, the
occupied sample unit nonresponse rate for the Census 2000 sample was
larger than the ACS three-year average estimate. Table A-1 in Appendix A
contains the ACS three-year average and Census 2000 sample unit
nonresponse rates (UNR) and occupied sample unit nonresponse rates
(OUNR) for each of the 36 counties. The counties whose differences are
not statistically significantly significant are marked with an "NS" in
the table.

Table 6 shows that, on average, the Census 2000 sample unit nonresponse
rate was 5.3 percent larger than the ACS three-year average sample unit
nonresponse rate. Since the margin of error for the difference is only
1.5 percent, the resulting confidence interval would not contain zero.
So, the average sample unit nonresponse rate difference is statistically
significant. For the occupied sample unit nonresponse rate, the Census
2000 sample rate was 3.5 percent larger than the ACS three-year average
rate. The margin of error for the occupied sample unit nonresponse rate
is only 1.3 percent. So, the average occupied sample unit nonresponse
rate is also statistically significantly different.

Figures C-2 and C-3 in Appendix C display the county-level sample unit
nonresponse rate and occupied sample unit nonresponse rate differences,
respectively, for all 36 counties through the use of one-dimensional
scatter plots. For these plots, differences between the ACS three-year
averages and the Census 2000 sample quality measures are located on the
vertical axis; counties are on the horizontal axis. We sorted counties
by their 100 percent count of census housing units. The sorts were in
ascending order, from left to right. For example, the difference for the
county with the smallest count is the left-most point in the plots,
while the difference for the county with the largest count is the
right-most point. We used a "jittering" process so that we could plot
the differences in this way. The "jittering" process assigned a unique
integer to each county so as to achieve this sort, where the county with
the smallest count received the smallest integer, etc.

Figure C-2 shows that nearly all of the sample unit nonresponse rates
for the ACS three-year averages were lower than the Census 2000 sample
estimates. For the most part, these differences are either centered
between --2 and 2, or around --6. Statistically significant differences
are indicated by an "X" on this plot.

Figure C-3 shows that nearly all of the occupied sample unit nonresponse
rates for the ACS three-year averages were lower than the Census 2000
sample estimates. For the most part, these differences ranged between
--8 and 2. Statistically significant differences are indicated by an "X"
on this plot.

The results presented in Table 5, Table 6, Appendix A, Figures C-2, and
Figure C-3, show that, in general, the ACS obtained more information
during followup operations than the census. These differences in unit
nonresponse rates could be a signal of higher nonresponse error in the
Census 2000 sample.

The larger Census 2000 sample unit nonresponse rates are not unexpected
because of differences between the census and ACS. The main emphasis of
the decennial census is to enumerate the U.S. population, and only
secondarily to collect long form sample data. In addition, temporary
enumerators collect census data while permanent, professional
interviewers collect ACS data. Census 2000 enumerated the nations'
population and collected detailed demographic information via the census
long form over the span of six months, and did not followup on items
left blank on mail returned questionnaires. In contrast, the sole focus
of the ACS is collecting "long form" data, using monthly samples with
three-month collection cycles, and the ACS conducts a followup of items
left blank on mail returned questionnaires. The census has to follow-up
on all non-responding units in the country in a tight time frame, making
it difficult for the census to obtain complete long form information,
especially if it is necessary to obtain information from neighbors. The
ACS, on the other hand, follows-up on only a sample of nonresponding
units, and does not allow information to be collected from neighbors.
All these differences between the census and ACS could contribute to the
differences in sample unit nonresponse rates.

*Number range CHAPTER3.2.2 Tract Comparisons*

This section contains the nonresponse rate comparisons for sample units
and occupied sample units for tracts. In this section we compare the ACS
three-year average and Census 2000 sample unit nonresponse rate and
occupied sample unit nonresponse rate differences for the tracts in the
34 counties by tract group, and then compare the differences when the
values are averaged across all the tracts in a group.

Table 7 shows the number of tracts with statistically significantly
different ACS three-year average and Census 2000 sample unit nonresponse
and occupied sample unit nonresponse rates for each of the five tract
groups. Table 8 shows the results of comparing the average of the tract
rates for each group.

+-------------------------+------+---------+-----------+-------------+
| **Table 7. Number of    |      |         |           |             |
| Tracts with             |      |         |           |             |
| Statistically           |      |         |           |             |
| Significantly Different |      |         |           |             |
| Nonresponse Rates for   |      |         |           |             |
| Sample Units and        |      |         |           |             |
| Occupied Sample Units,  |      |         |           |             |
| by Tract Group ^C^**    |      |         |           |             |
+=========================+======+=========+===========+=============+
| **Quality Measure**     | **T  | *       | **Number  | **Number of |
|                         | ract | *Number | of Tracts | Tracts      |
|                         | Gr   | of      | Stat      | St          |
|                         | oup^ | Tracts  | istically | atistically |
|                         | N^** | Not     | Sign      | Si          |
|                         |      | Statis  | ificantly | gnificantly |
|                         |      | tically | Different | Different   |
|                         |      | Signif  | with ACS  | with Census |
|                         |      | icantly | \>        | \> ACS**    |
|                         |      | Diff    | Census**  |             |
|                         |      | erent** |           |             |
+-------------------------+------+---------+-----------+-------------+
| Sample unit nonresponse | 1    | 162     | 3         | 42          |
| rate                    |      |         |           |             |
+-------------------------+------+---------+-----------+-------------+
|                         | 2    | 569     | 0         | 23          |
+-------------------------+------+---------+-----------+-------------+
|                         | 3    | 510     | 1         | 69          |
+-------------------------+------+---------+-----------+-------------+
|                         | 4    | 388     | 0         | 13          |
+-------------------------+------+---------+-----------+-------------+
|                         | 5    | 392     | 0         | 78          |
+-------------------------+------+---------+-----------+-------------+
| Occupied sample unit    | 1    | 193     | 0         | 14          |
| nonresponse rate        |      |         |           |             |
+-------------------------+------+---------+-----------+-------------+
|                         | 2    | 580     | 0         | 12          |
+-------------------------+------+---------+-----------+-------------+
|                         | 3    | 533     | 2         | 45          |
+-------------------------+------+---------+-----------+-------------+
|                         | 4    | 392     | 0         | 9           |
+-------------------------+------+---------+-----------+-------------+
|                         | 5    | 398     | 0         | 72          |
+-------------------------+------+---------+-----------+-------------+
| N -- Note, group 1      |      |         |           |             |
| contains 207 tracts,    |      |         |           |             |
| group 2 contains 592    |      |         |           |             |
| tracts, group 3         |      |         |           |             |
| contains 580 tracts,    |      |         |           |             |
| group 4 contains 401    |      |         |           |             |
| tracts, and group 5     |      |         |           |             |
| contains 470 tracts.    |      |         |           |             |
|                         |      |         |           |             |
| C -- Comparisons are    |      |         |           |             |
| based on a non-random   |      |         |           |             |
| sample of counties      |      |         |           |             |
+-------------------------+------+---------+-----------+-------------+

+-----------------------+------+------+------+----------+----------+---+
| **Table 8. Comparison |      |      |      |          |          |   |
| of Nonresponse Rates  |      |      |      |          |          |   |
| for Sample Units and  |      |      |      |          |          |   |
| Occupied Sample       |      |      |      |          |          |   |
| Units: ACS Three-year |      |      |      |          |          |   |
| Averages and Census   |      |      |      |          |          |   |
| 2000 Sample           |      |      |      |          |          |   |
| Estimates, Tract      |      |      |      |          |          |   |
| Group Averages**      |      |      |      |          |          |   |
+=======================+======+======+======+==========+==========+===+
| **Quality Measure**   | **T  | *    | **Ce | **Diffe  | **Margin |   |
|                       | ract | *ACS | nsus | rence^D^ | of       |   |
|                       | Gr   | A    | A    | of       | Er       |   |
|                       | oup^ | vera | vera | Av       | ror^C^** |   |
|                       | N^** | ge** | ge** | erages** |          |   |
+-----------------------+------+------+------+----------+----------+---+
| Sample unit           | 1    | 4.3% | 1    | -6.4%    | ± 1.0%   |   |
| nonresponse rate      |      |      | 0.7% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 2    | 4.6% | 9.4% | -4.8%    | ± 0.6%   |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 3    | 4.4% | 8.9% | -4.5%    | ± 0.4%   |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 4    | 5.9% | 1    | -9.9%    | ± 1.0%   |   |
|                       |      |      | 5.7% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 5    | 4.9% | 1    | -6.9%    | ± 0.7%   |   |
|                       |      |      | 1.8% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
| Occupied sample unit  | 1    | 5.4% | 9.3% | -3.9%    | ± 0.8%   |   |
| nonresponse rate      |      |      |      |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 2    | 5.0% | 8.8% | -3.8%    | ± 0.5%   |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 3    | 4.7% | 8.5% | -3.8%    | ± 0.4%   |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 4    | 6.5% | 1    | -9.1%    | ± 1.0%   |   |
|                       |      |      | 5.6% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
|                       | 5    | 5.4% | 1    | -7.0%    | ± 0.7%   |   |
|                       |      |      | 2.4% |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
| N -- Note, group 1    |      |      |      |          |          |   |
| contains 207 tracts,  |      |      |      |          |          |   |
| group 2 contains 592  |      |      |      |          |          |   |
| tracts, group 3       |      |      |      |          |          |   |
| contains 580 tracts,  |      |      |      |          |          |   |
| group 4 contains 401  |      |      |      |          |          |   |
| tracts, and group 5   |      |      |      |          |          |   |
| contains 470 tracts.  |      |      |      |          |          |   |
+-----------------------+------+------+------+----------+----------+---+
| D -- The difference   |      |      |      |          |          |   |
| is the ACS average    |      |      |      |          |          |   |
| minus the Census 2000 |      |      |      |          |          |   |
| average.              |      |      |      |          |          |   |
|                       |      |      |      |          |          |   |
| C -- This comparison  |      |      |      |          |          |   |
| is based on a         |      |      |      |          |          |   |
| non-random sample of  |      |      |      |          |          |   |
| counties              |      |      |      |          |          |   |
+-----------------------+------+------+------+----------+----------+---+

Table 7 shows that more than 10 percent of the tract differences in
groups 1, 3, and 5 are statistically significant for the sample unit
nonresponse rates. For group 1, 22.0 percent (45 out of 207) of the
tract differences are statistically significant. For group 2, 3.9
percent (23 out of 592) of the tract differences are statistically
significant. For group 3, 12.1 percent (70 out of 580) of the tract
differences are statistically significant. For group 4, 3.2 percent (13
out of 401) of the tract differences are statistically significant. For
group 5, 16.6 percent (78 out of 470) of the tract differences are
statistically significant. So, we see the most statically significant
differences for the tracts in small counties (group 1), tracts with
large populations in medium counties (group 3), and the tracts with
large populations in counties with large populations (group 5). In
addition, for all of the statistically significant differences for
groups 2, 4, and 5, the Census 2000 sample unit nonresponse rates were
larger than the ACS three-year average rates. For group 1, for 42 out of
the 45 statistically significant differences, the census sample unit
nonresponse rate was larger than the ACS sample unit nonresponse rate.
For group 3, for 69 out of the 70 statistically significant differences,
the census sample unit nonresponse rate was larger than the ACS sample
unit nonresponse rate. So, for groups 1, 3, and 5, the ACS obtained more
information during followup operations.

Table 7 also shows that for the occupied sample unit nonresponse rate,
the only group to yield more than 10 percent of their tract differences
statistically significant is group 5. For group 1, 6.8 percent (14 out
of 207) of the tract differences are statistically significant. For
group 2, 2.0 percent (12 out of 592) of the tract differences are
statistically significant. For group 3, 8.1 percent (47 out of 580) of
the tract differences are statistically significant. For group 4, 2.2
percent (9 out of 401) of the tract differences are statistically
significant. For group 5, 15.3 percent (72 out of 470) of the tract
differences are statistically significant. So, we see the most
statistically significant differences occur for the tracts with large
populations in counties with large populations (group 5). In addition,
for all of the statistically significant differences for groups 1, 2, 4,
and 5, the Census 2000 occupied sample unit nonresponse rates were
larger than the ACS three-year average rates. For group 3, for 45 out of
the 47 statistically significant differences, the census occupied sample
unit nonresponse rate was larger than the ACS occupied sample unit
nonresponse rate. So, for group 5, the ACS obtained more information
during followup operations.

Table 8 shows that for all five groups the ACS, on average, received
more information during followup operations. The average tract census
sample unit nonresponse rate and occupied sample unit nonresponse rate
for all five groups is larger than the average tract ACS sample unit
nonresponse rate and occupied sample unit nonresponse rate. The margin
of error for each rate and each of the five groups was less than the
absolute value of the difference between the averages. So, the
difference between the average is statistically significantly different
for all five groups for both rates.

Figures D-2 and D-3 in Appendix D display tract-level sample unit
nonresponse rate and occupied sample unit nonresponse rate differences
through the use of one-dimensional scatter plots. We grouped all of the
tract-level differences by tract group. For these plots, differences
between the ACS three-year average and Census 2000 sample quality
measures are located on the vertical axis; tracts and tract groups are
on the horizontal axis. We sorted tracts within each tract group by
their 100 percent count of census housing units. The sorts were in
ascending order, from left to right, within each tract group. For
example, the difference for the tract with the smallest count is the
left-most point within each tract group, while the difference for the
tract with the largest count is the right-most point within each tract
group. We used a "jittering" process so that we could plot the
differences in this way. Within each tract group, the "jittering"
process assigned a unique integer to each tract so as to achieve this
sort, where the tract with the smallest count received the smallest
integer, etc.

Figure D-2 shows that a majority of the sample unit nonresponse rates
for the ACS three-year averages are lower than the Census 2000 sample
estimates. The majority of the differences are between --30 and 10.
Statistically significant differences are indicated by an "X" on this
plot.

Figure D-3 shows that, for each tract group, a majority of the occupied
sample unit nonresponse rates for the ACS three-year averages are lower
than the Census 2000 sample estimates. The majority of the differences
are between --30 and 10. Statistically significant differences are
indicated by an "X" on this plot.

The results presented in Table 7, Table 8, Figure D-2, and Figure D-3
show that on average, the ACS collected information from a higher
percentage of the units in its sample than the census. This difference
in unit nonresponse could be a signal of higher nonresponse error in the
census. These results were anticipated due to the design of ACS
operations as discussed at the end of section 3.2.1.

**3.3 Item Allocation Rates**

We measure item nonresponse to help determine potential nonsampling
error. Item nonresponse is the extent to which a required answer to an
individual questionnaire item is missing. Items on a questionnaire can
be left unanswered for a variety of reasons. Respondents may choose not
to answer an item because they do not see the need to cooperate, view
the item as too personal, do not have time to answer all items on the
questionnaire, misunderstand the wording on the questionnaire,
misunderstand the various paths in a questionnaire, etcetera. In
addition, items left blank on a questionnaire may differ between the
housing units with mailed in forms, and housing units whose data has to
be collected through field operations. For whatever reason an item is
left blank, blank items can affect the quality of the final survey
estimates.

To measure item nonresponse, we calculated item allocation (or
imputation) rates. They are the percent of the total number of persons
or housing units required to respond to the item for which the value of
that item was allocated (that is, imputed). When an item on a
questionnaire is missing or inconsistent, that item is edited and its
value imputed from a different housing unit or person record. Both the
ACS and the census used "nearest neighbor" hot deck matrices to identify
the housing unit or person record whose value for a particular item on
the questionnaire was assigned to the missing or inconsistent item on
the other questionnaire. If the actual values of the missing
characteristics differ from the responses used in the imputation, the
resulting data can be biased.

Summary item allocation rates are provided for each of the 36 ACS
counties, and for tracts in the 34 ACS tract-level comparison counties.
At the county level, the summary item allocation rates are also broken
out by response mode. They are not broken out by response mode at the
tract level because of small sample sizes at the tract level. The
county-level comparison results are presented in section 3.3.1, and the
tract-level comparison results are presented in section 3.3.2.

The response modes are self-response or interviewer-response.
Self-response means that the household data came from a mail return, and
interviewer-response means that an interviewer or enumerator obtained
the data with the use of a follow-up form or instrument. For Census
2000, the follow-up operations were Nonresponse Follow-Up and Coverage
Improvement Follow-up. For the ACS, the follow-up operations were
Computer Assisted Telephone Interviewing (CATI) and Computer Assisted
Personal Interviewing (CAPI).

Item allocation rates were calculated for items that appeared on both
the ACS and Census 2000 long form questionnaires (54 population items,
29 occupied housing unit items, and 12 vacant housing unit items). While
the questions may not all have been identical, they were comparable. The
Census 2000 sample item allocation rates are based on the final-weighted
allocations made by the census edit and allocation process on all
records placed in the Census 2000 sample (on the Census 2000 Sample
Census Edited File). The ACS three-year average item allocation rates
are based on the final-weighted allocations made by the ACS edit and
allocation process. The universe for the census and ACS item allocation
rates are all persons or housing units who were required to respond to
the item.

Summary item allocation rates provide overall measures of item
nonresponse, and summarize the population and housing item allocation
rates. They show overall patterns in the data. However, they also
obscure differences among the individual items.

We calculated the summary item allocation rates by adding the numerators
of the item allocation rates, adding the denominators of the item
allocation rates, and then dividing the sum of the numerators by the sum
of the denominators. We used these summary item allocation rates instead
of averaging the item allocation rates to ensure that the proportion of
respondents required to respond to that item weighted each item. The
first summary item allocation rate summed the 54 population item
allocation rate numerators and denominators. The second summed the 29
occupied housing unit item allocation rate numerators and denominators.
The third summed the 12 vacant housing unit item allocation rate
numerators and denominators. The fourth summed the 54 population item
allocation rate and 29 occupied housing unit item allocation rate
numerators and denominators.

The Census 2000 sample item allocation rates are:

-   Total = (Census 2000 sample final weighted total persons or housing
    units with that item allocated / Census 2000 sample final weighted
    total persons or housing units in the universe) × 100

-   Self-response = (Census 2000 sample final weighted persons in
    self-responding households or occupied housing units with that item
    allocated / Census 2000 sample final weighted persons in
    self-responding households or occupied housing units in the
    universe) × 100

-   Interview-response = (Census 2000 sample final weighted persons in
    households or housing units enumerated by field operations with that
    item allocated / Census 2000 sample final weighted persons in
    households or housing units enumerated by field operations in the
    universe) × 100

    The ACS three-year average sample item allocation rates are:

```{=html}
<!-- -->
```
-   Total = (ACS final weighted total persons or housing units with that
    item allocated / ACS final weighted total persons or housing units
    in the universe) × 100

-   Self-response = (ACS final weighted persons in self-responding
    households or occupied housing units with that item allocated / ACS
    final weighted persons in self-responding households or occupied
    housing units in the universe) × 100

-   Interview-response = (ACS final weighted persons in households or
    housing units interviewed by CATI or CAPI with that item allocated /
    ACS final weighted persons in households or housing units
    interviewed by CATI or CAPI in the universe) × 100

*Number range CHAPTER3.3.1 County Comparisons*

This section contains the summary item allocation rate comparison
results for the counties. In this section we compare the ACS three-year
average and Census 2000 sample summary item allocation rate differences
for each of the 36 counties, and then compare the differences when the
values are averaged across all the counties.

Table 9 shows the number of counties with statistically significantly
different item allocation rates for the ACS three-year average and
Census 2000 sample. Table 10 shows the results of comparing the summary
item allocation rates averaged across the 36 counties.

+-------------------------------+----------+------------+-------------+
| **Table 9. Number of Counties |          |            |             |
| with Statistically            |          |            |             |
| Significantly Different       |          |            |             |
| Summary Item Allocation Rates |          |            |             |
| ^C^**                         |          |            |             |
+===============================+==========+============+=============+
| **Quality Measure**           | **Number | **Number   | **Number of |
|                               | of 36    | of 36      | 36 Counties |
|                               | Counties | Counties   | St          |
|                               | Not      | Sta        | atistically |
|                               | Stati    | tistically | Si          |
|                               | stically | Sig        | gnificantly |
|                               | Signi    | nificantly | Different   |
|                               | ficantly | Different  | with Census |
|                               | Dif      | with ACS   | \> ACS**    |
|                               | ferent** | \>         |             |
|                               |          | Census**   |             |
+-------------------------------+----------+------------+-------------+
| ## Summary pop                |          |            |             |
| ulation item allocation rates |          |            |             |
+-------------------------------+----------+------------+-------------+
| Total                         | 2        | 0          | 34          |
+-------------------------------+----------+------------+-------------+
| Self-response                 | 17       | 0          | 19          |
+-------------------------------+----------+------------+-------------+
| Interviewer-response          | 3        | 0          | 33          |
+-------------------------------+----------+------------+-------------+
| ## Summary housi              |          |            |             |
| ng unit item allocation rates |          |            |             |
+-------------------------------+----------+------------+-------------+
| Total occupied housing unit   | 0        | 0          | 36          |
+-------------------------------+----------+------------+-------------+
| Total vacant housing unit     | 24       | 10         | 2           |
+-------------------------------+----------+------------+-------------+
| Self-response occupied        | 2        | 0          | 34          |
| housing unit                  |          |            |             |
+-------------------------------+----------+------------+-------------+
| Interviewer-response occupied | 1        | 0          | 35          |
| housing unit                  |          |            |             |
+-------------------------------+----------+------------+-------------+
| **Summary population and      |          |            |             |
| occupied housing unit item    |          |            |             |
| allocation rates**            |          |            |             |
+-------------------------------+----------+------------+-------------+
| Total                         | 0        | 0          | 36          |
+-------------------------------+----------+------------+-------------+
| Self-response                 | 5        | 0          | 31          |
+-------------------------------+----------+------------+-------------+
| Interviewer-response          | 1        | 0          | 35          |
+-------------------------------+----------+------------+-------------+
| C -- Comparisons are based on |          |            |             |
| a non-random sample of        |          |            |             |
| counties                      |          |            |             |
+-------------------------------+----------+------------+-------------+

+-----------------------------------+------+------+--------+----------+
| **Table 10. Comparison of Summary |      |      |        |          |
| Item Allocation Rates: ACS        |      |      |        |          |
| Three-year Averages and Census    |      |      |        |          |
| 2000 Sample Estimates, County     |      |      |        |          |
| Averages**                        |      |      |        |          |
+===================================+======+======+========+==========+
| **Quality Measure**               | *    | **Ce | **D    | **Margin |
|                                   | *ACS | nsus | iffere | of       |
|                                   | A    | A    | nce^D^ | Er       |
|                                   | vera | vera | of     | ror^C^** |
|                                   | ge** | ge** | Aver   |          |
|                                   |      |      | ages** |          |
+-----------------------------------+------+------+--------+----------+
| **Summary population item         |      |      |        |          |
| allocation rates**                |      |      |        |          |
+-----------------------------------+------+------+--------+----------+
| Total                             | 6.5% | 1    | -4.7%  | ± 0.6%   |
|                                   |      | 1.2% |        |          |
+-----------------------------------+------+------+--------+----------+
| Self-response                     | 8.9% | 1    | -1.3%  | ± 0.8%   |
|                                   |      | 0.2% |        |          |
+-----------------------------------+------+------+--------+----------+
| Interviewer-response              | 4.2% | 1    | -9.8%  | ± 1.1%   |
|                                   |      | 4.0% |        |          |
+-----------------------------------+------+------+--------+----------+
| ## Summary h                      |      |      |        |          |
| ousing unit item allocation rates |      |      |        |          |
+-----------------------------------+------+------+--------+----------+
| Total occupied housing units      | 7.7% | 1    | -8.0%  | ± 0.8%   |
|                                   |      | 5.8% |        |          |
+-----------------------------------+------+------+--------+----------+
| Total vacant housing units        | 2    | 1    | 3.4%   | ± 2.8%   |
|                                   | 3.2% | 9.8% |        |          |
+-----------------------------------+------+------+--------+----------+
| Self-response occupied housing    | 7.5% | 1    | -7.5%  | ± 1.0%   |
| unit                              |      | 5.0% |        |          |
+-----------------------------------+------+------+--------+----------+
| Interviewer-response occupied     | 8.8% | 1    | -10.1% | ± 1.3%   |
| housing units                     |      | 8.9% |        |          |
+-----------------------------------+------+------+--------+----------+
| **Summary population and occupied |      |      |        |          |
| housing unit item allocation      |      |      |        |          |
| rates**                           |      |      |        |          |
+-----------------------------------+------+------+--------+----------+
| Total                             | 6.9% | 1    | -5.9%  | ± 0.6%   |
|                                   |      | 2.8% |        |          |
+-----------------------------------+------+------+--------+----------+
| Self-response                     | 8.5% | 1    | -3.5%  | ± 0.9%   |
|                                   |      | 1.9% |        |          |
+-----------------------------------+------+------+--------+----------+
| Interviewer-response              | 5.8% | 1    | -10.0% | ± 1.1%   |
|                                   |      | 5.7% |        |          |
+-----------------------------------+------+------+--------+----------+
| D -- The difference is the ACS    |      |      |        |          |
| average minus the Census 2000     |      |      |        |          |
| average.                          |      |      |        |          |
|                                   |      |      |        |          |
| C -- This comparison is based on  |      |      |        |          |
| a non-random sample of counties   |      |      |        |          |
+-----------------------------------+------+------+--------+----------+

Table 9 and Table 10 show that except for the summary total vacant
housing unit item allocation rates, the ACS had lower item allocation
rates.

Table 9 shows that, for most of the quality measures, over 80 percent of
the 36 counties exhibited statistically significantly higher Census 2000
summary item allocation rates. There were two exceptions. One exception
was for summary population item allocation rates, self-response mode;
almost half of the counties (17 of 36) showed no statistically
significant differences between the ACS and Census 2000 rates. The
second exception was for summary housing unit item allocation rates for
total vacant housing units. Two-thirds of the counties (24 of 36)
exhibited no statistically significant differences between ACS and
Census 2000 summary housing unit item allocation rates. Additionally, 10
of the remaining 12 counties exhibited statistically significantly
higher ACS summary housing unit item allocation rates. Table A-2 in
Appendix A contains the summary population item allocation rates for the
ACS three-year averages and Census 2000 sample for each of the 36
counties. Table A-3 in Appendix A contains the summary housing unit item
allocation rates for the ACS three-year averages and Census 2000 sample
for each of the 36 counties. Table A-4 in Appendix A contains the
summary population and occupied housing unit item allocation rates for
the ACS three-year averages and Census 2000 sample for each of the 36
counties. In each of these tables, the counties whose differences are
not statistically significant are marked with an "NS".

Table 10 shows, that for all of the summary item allocation rates,
except the average summary vacant housing unit item allocation rate, the
census average rate is larger than the ACS average rates. For the
average summary vacant housing unit item allocation rates, the ACS
average rate is larger than the census average rate. In addition, none
of the margin of errors are greater than the absolute values of the
differences. So, all of the average differences are statistically
significantly different.

Figures C-4, C-5, and C-6 in Appendix C display the county-level summary
population item allocation rate, summary housing unit item allocation
rate, and summary population and occupied housing unit item allocation
rate differences, respectively, for all 36 counties. The figures display
these differences through the use of one-dimensional scatter plots. For
these plots, differences between the ACS three-year averages and the
Census 2000 sample quality measures are located on the vertical axis;
counties by quality measure are on the horizontal axis. We sorted
counties by their We sorted counties within quality measure by their 100
percent count of census housing units. The sorts were in ascending
order, from left to right. For example, the difference for the county
with the smallest count is the left-most point in each quality measure
in each graph, while the difference for the county with the largest
count is the right-most point in each quality measure in each graph. We
used a "jittering" process so that we could plot the differences in this
way. Within each quality measure, the "jittering" process assigned a
unique integer to each county so as to achieve this sort, where the
county with the smallest count received the smallest integer, etc.

Figures C-4, C-5, and C-6 show that, except for the summary vacant
housing unit item nonresponse rates, the census rates are almost always
larger than the ACS rates. The statistically significant differences are
identified by an "X" on these plots.

The results presented in Table 9, Table 10, Appendix A and Appendix C
show that for population and occupied housing unit items, the ACS had
less item nonresponse as measured by the item allocation rates. For the
vacant housing unit items, the census had less item nonresponse. These
higher rates can indicate possible nonresponse error and bias in the
estimates.

Given the operational differences between the ACS and census, the larger
Census 2000 sample summary item allocation rates would have been
expected. The ACS procedures are designed to minimize the item
nonresponse and subsequently the need for item allocation. The main
emphasis of the decennial census is to enumerate the U.S. population,
and only secondarily to collect long form sample data. In addition,
temporary enumerators collect census data while permanent, professional
interviewers collect ACS data. Census 2000 enumerated the nations'
population and collected detailed demographic information via the census
long form over the span of six months, and did not followup on items
left blank on mail returned questionnaires. In contrast, the sole focus
of the ACS is collecting "long form" data, using monthly samples with
three-month collection cycles, and conducting a followup of items left
blank on mail returned questionnaires. The census follows up on all
non-responding units in the country in a tight time frame, making it
difficult for the census to obtain complete long form information,
especially if it is necessary to obtain information from neighbors. The
ACS, on the other hand, follows-up on only a sample of nonresponding
units, and does not allow information to be collected from neighbors.
All these differences between the census and ACS could contribute to the
differences in summary item allocation rates. The reasons for the
differences in the vacant summary item allocation rates will need to be
explored further.

*Number range CHAPTER3.3.2 Tract Comparisons*

This section contains the tract level summary item allocation rate
comparison results. In this section we compare the ACS three-year
average and Census 2000 sample summary item allocation rate differences
for the tracts in the 34 counties by tract group, and then compare the
differences when the values are averaged across all counties by tract
group. We only compared the total summary item allocation rates for the
tracts. We did not compare the self-response or interviewer-response
summary item allocation rates because of small sample sizes.

Table 11 shows the number of tracts with statistically significantly
different ACS three-year average and Census 2000 sample summary item
allocation rates for each of the five tract groups. Table 12 shows the
results of comparing the average of the tract summary item allocation
rates for each group.

+--------------------+------+----------+-------------+-------------+---+
| **Table 11. Number |      |          |             |             |   |
| of Tracts with     |      |          |             |             |   |
| Statistically      |      |          |             |             |   |
| Significantly      |      |          |             |             |   |
| Different Summary  |      |          |             |             |   |
| Item Allocation    |      |          |             |             |   |
| Rates, by Tract    |      |          |             |             |   |
| Group ^C^**        |      |          |             |             |   |
+====================+======+==========+=============+=============+===+
| **Quality          | **T  | **Number | **Number of | **Number of |   |
| Measure**          | ract | of       | Tracts      | Tracts      |   |
|                    | Gr   | Tracts   | St          | St          |   |
|                    | oup^ | Not      | atistically | atistically |   |
|                    | N^** | Stati    | Si          | Si          |   |
|                    |      | stically | gnificantly | gnificantly |   |
|                    |      | Signi    | Different   | Different   |   |
|                    |      | ficantly | with ACS \> | with Census |   |
|                    |      | Dif      | Census**    | \> ACS**    |   |
|                    |      | ferent** |             |             |   |
+--------------------+------+----------+-------------+-------------+---+
| Summary total      | 1    | 174      | 0           | 33          |   |
| population item    |      |          |             |             |   |
| allocation rate    |      |          |             |             |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 2    | 504      | 0           | 88          |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 3    | 453      | 0           | 127         |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 4    | 310      | 0           | 91          |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 5    | 327      | 0           | 143         |   |
+--------------------+------+----------+-------------+-------------+---+
| Summary total      | 1    | 145      | 0           | 62          |   |
| occupied housing   |      |          |             |             |   |
| unit item          |      |          |             |             |   |
| allocation rate    |      |          |             |             |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 2    | 558      | 0           | 34          |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 3    | 474      | 0           | 106         |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 4    | 380      | 0           | 21          |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 5    | 415      | 0           | 55          |   |
+--------------------+------+----------+-------------+-------------+---+
| Summary total      | 1    | 201      | 1           | 2           |   |
| vacant housing     |      |          |             |             |   |
| unit item          |      |          |             |             |   |
| allocation rate    |      |          |             |             |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 2    | 507      | 1           | 1           |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 3    | 545      | 1           | 0           |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 4    | 348      | 3           | 0           |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 5    | 449      | 0           | 2           |   |
+--------------------+------+----------+-------------+-------------+---+
| Summary total      | 1    | 128      | 0           | 79          |   |
| population and     |      |          |             |             |   |
| occupied housing   |      |          |             |             |   |
| unit item          |      |          |             |             |   |
| allocation rate    |      |          |             |             |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 2    | 463      | 0           | 129         |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 3    | 374      | 0           | 206         |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 4    | 269      | 0           | 132         |   |
+--------------------+------+----------+-------------+-------------+---+
|                    | 5    | 275      | 0           | 195         |   |
+--------------------+------+----------+-------------+-------------+---+
| N -- Note, group 1 |      |          |             |             |   |
| contains 207       |      |          |             |             |   |
| tracts, group 2    |      |          |             |             |   |
| contains 592       |      |          |             |             |   |
| tracts, group 3    |      |          |             |             |   |
| contains 580       |      |          |             |             |   |
| tracts, group 4    |      |          |             |             |   |
| contains 401       |      |          |             |             |   |
| tracts, and group  |      |          |             |             |   |
| 5 contains 470     |      |          |             |             |   |
| tracts. For vacant |      |          |             |             |   |
| units, group 1     |      |          |             |             |   |
| contains 204       |      |          |             |             |   |
| tracts, group 2    |      |          |             |             |   |
| contains 509       |      |          |             |             |   |
| tracts, group 3    |      |          |             |             |   |
| contains 546       |      |          |             |             |   |
| tracts, group 4    |      |          |             |             |   |
| contains 351       |      |          |             |             |   |
| tracts, and group  |      |          |             |             |   |
| 5 contains 451     |      |          |             |             |   |
| tracts.            |      |          |             |             |   |
|                    |      |          |             |             |   |
| C -- Comparisons   |      |          |             |             |   |
| are based on a     |      |          |             |             |   |
| non-random sample  |      |          |             |             |   |
| of counties        |      |          |             |             |   |
+--------------------+------+----------+-------------+-------------+---+

+------------------+-------+-------+-------+------------+-----------+
| **Table 12.      |       |       |       |            |           |
| Comparison of    |       |       |       |            |           |
| Summary Item     |       |       |       |            |           |
| Allocation       |       |       |       |            |           |
| Rates: ACS       |       |       |       |            |           |
| Three-year       |       |       |       |            |           |
| Averages and     |       |       |       |            |           |
| Census 2000      |       |       |       |            |           |
| Sample           |       |       |       |            |           |
| Estimates, Tract |       |       |       |            |           |
| Group Averages** |       |       |       |            |           |
+==================+=======+=======+=======+============+===========+
| **Quality        | **    | **ACS | **C   | **Dif      | **Margin  |
| Measure**        | Tract | Aver  | ensus | ference^D^ | of        |
|                  | Group | age** | Aver  | of         | E         |
|                  | ^N^** |       | age** | Averages** | rror^C^** |
+------------------+-------+-------+-------+------------+-----------+
| Summary total    | 1     | 6.9%  | 11.7% | -4.8%      | 0.5%      |
| population item  |       |       |       |            |           |
| allocation rate  |       |       |       |            |           |
+------------------+-------+-------+-------+------------+-----------+
|                  | 2     | 6.5%  | 10.6% | -4.1%      | 0.3%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 3     | 6.6%  | 10.9% | -4.3%      | 0.3%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 4     | 7.4%  | 13.8% | -6.4%      | 0.5%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 5     | 7.1%  | 12.3% | -5.2%      | 0.4%      |
+------------------+-------+-------+-------+------------+-----------+
| Summary total    | 1     | 7.7%  | 15.7% | -8.0%      | 0.5%      |
| occupied housing |       |       |       |            |           |
| unit item        |       |       |       |            |           |
| allocation rate  |       |       |       |            |           |
+------------------+-------+-------+-------+------------+-----------+
|                  | 2     | 6.7%  | 13.3% | -6.6%      | 0.3%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 3     | 7.3%  | 14.1% | -6.8%      | 0.3%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 4     | 7.5%  | 16.9% | -9.4%      | 0.6%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 5     | 7.4%  | 15.9% | -8.5%      | 0.5%      |
+------------------+-------+-------+-------+------------+-----------+
| Summary total    | 1     | 22.0% | 20.3% | 1.7%       | ^NS^ 1.8% |
| vacant housing   |       |       |       |            |           |
| unit item        |       |       |       |            |           |
| allocation rate  |       |       |       |            |           |
+------------------+-------+-------+-------+------------+-----------+
|                  | 2     | 15.7% | 14.3% | 1.4%       | 1.2%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 3     | 16.2% | 13.9% | 2.3%       | 1.1%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 4     | 14.9% | 15.6% | -0.7%      | ^NS^ 1.5% |
+------------------+-------+-------+-------+------------+-----------+
|                  | 5     | 13.0% | 14.8% | -1.7%      | 1.0%      |
+------------------+-------+-------+-------+------------+-----------+
| Summary total    | 1     | 7.2%  | 13.1% | -5.9%      | 0.5%      |
| population and   |       |       |       |            |           |
| occupied housing |       |       |       |            |           |
| unit item        |       |       |       |            |           |
| allocation rate  |       |       |       |            |           |
+------------------+-------+-------+-------+------------+-----------+
|                  | 2     | 6.5%  | 11.5% | -5.0%      | 0.3%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 3     | 6.9%  | 12.0% | -5.2%      | 0.3%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 4     | 7.4%  | 14.9% | -7.4%      | 0.5%      |
+------------------+-------+-------+-------+------------+-----------+
|                  | 5     | 7.2%  | 13.5% | -6.4%      | 0.4%      |
+------------------+-------+-------+-------+------------+-----------+
| N -- Note, group |       |       |       |            |           |
| 1 contains 207   |       |       |       |            |           |
| tracts, group2   |       |       |       |            |           |
| contains 592     |       |       |       |            |           |
| tracts, group 3  |       |       |       |            |           |
| contains 580     |       |       |       |            |           |
| tracts, group 4  |       |       |       |            |           |
| contains 401     |       |       |       |            |           |
| tracts, and      |       |       |       |            |           |
| group 5 contains |       |       |       |            |           |
| 470 tracts. For  |       |       |       |            |           |
| vacant units,    |       |       |       |            |           |
| group 1 contains |       |       |       |            |           |
| 204 tracts,      |       |       |       |            |           |
| group 2 contains |       |       |       |            |           |
| 509 tracts,      |       |       |       |            |           |
| group 3 contains |       |       |       |            |           |
| 546 tracts,      |       |       |       |            |           |
| group 4 contains |       |       |       |            |           |
| 351 tracts, and  |       |       |       |            |           |
| group 5 contains |       |       |       |            |           |
| 451 tracts.      |       |       |       |            |           |
+------------------+-------+-------+-------+------------+-----------+
| D -- The         |       |       |       |            |           |
| difference is    |       |       |       |            |           |
| the ACS average  |       |       |       |            |           |
| minus the Census |       |       |       |            |           |
| 2000 average.    |       |       |       |            |           |
|                  |       |       |       |            |           |
| C -- This        |       |       |       |            |           |
| comparison is    |       |       |       |            |           |
| based on a       |       |       |       |            |           |
| non-random       |       |       |       |            |           |
| sample of        |       |       |       |            |           |
| counties         |       |       |       |            |           |
|                  |       |       |       |            |           |
| NS -- The ACS    |       |       |       |            |           |
| three-year       |       |       |       |            |           |
| average and      |       |       |       |            |           |
| Census 2000      |       |       |       |            |           |
| sample quality   |       |       |       |            |           |
| measure are not  |       |       |       |            |           |
| statistically    |       |       |       |            |           |
| significantly    |       |       |       |            |           |
| different for    |       |       |       |            |           |
| this county.     |       |       |       |            |           |
+------------------+-------+-------+-------+------------+-----------+

Some tracts were excluded from the summary total vacant housing unit
item allocation rate comparison. For these tracts, there is no summary
total vacant housing unit item allocation rate for the Census 2000
sample because the denominator or universe of the census rate is zero.
For these tracts, the ACS had at least one vacant housing unit in one of
the three years. For group 2, 16 tracts were removed from the
comparison. For group 4, 14 tracts were removed.

Table 11 shows that for the summary population item allocation rates,
summary occupied housing unit item allocation rates, and the summary
population and occupied housing unit item allocation rates, tracts in
each group had ACS and Census 2000 rates that were either not
statistically significantly different or had statistically significantly
higher Census 2000 rates. The proportion of tracts in each group with
statistically significantly higher Census 2000 rates ranged from 5.2
percent (summary total occupied housing unit item allocation rate, tract
group 4) to 41.5 percent (summary total population and occupied housing
unit item allocation rate, tract group 5). In addition, Table 12 shows
that all of the average Census 2000 sample rates for these groups and
summary item allocation rates are statistically significantly larger
than the average ACS three-year average rate.

For the summary vacant housing unit item allocation rates, Table 11
shows that almost all of the tracts within all five tract groups
exhibited no statistically significant differences between the ACS and
Census 2000 rates. Of the tracts with statistically significant
differences, six exhibited higher ACS rates while five exhibited higher
Census 2000 rates. Table 12 shows no statistically significant
differences between the average ACS and Census 2000 summary vacant
housing unit item allocation rates for tract groups 1 and 4. Table 12
also shows that the average ACS rates are statistically significantly
higher for tract groups 2 and 3 while the average Census 2000 rates are
statistically significantly higher for tract group 5.

Figures D-4, D-5, D-6, and D-7 in Appendix D display tract-level summary
item allocation rate differences rate differences through the use of
one-dimensional scatter plots. We grouped all of the tract-level
differences by tract group. For these plots, differences between the ACS
three-year average and Census 2000 sample quality measures are located
on the vertical axis; tracts and tract groups are on the horizontal
axis. We sorted tracts within each tract group by their 100 percent
count of census housing units. The sorts were in ascending order, from
left to right, within each tract group. For example, the difference for
the tract with the smallest count is the left-most point within each
tract group, while the difference for the tract with the largest count
is the right-most point within each tract group. We used a "jittering"
process so that we could plot the differences in this way. Within each
tract group, the "jittering" process assigned a unique integer to each
tract so as to achieve this sort, where the tract with the smallest
count received the smallest integer, etc.

Figure D-4 displays the tract-level summary population item allocation
rate differences, by tract group. It shows that for each group, for a
majority of the summary population item allocation rates, the ACS
three-year averages are lower than the Census 2000 sample estimates. The
majority of the differences are between --15 and 5. Statistically
significant differences are indicated by an "X" on these scatter plots.

Figure D-5 displays the tract-level summary occupied housing unit item
allocation rate differences, by tract group. It shows that for each
group, for a majority of the summary occupied housing unit item
allocation rates, the ACS 3-year averages are lower than the Census 2000
sample estimates. The majority of the differences are between --15 and 0
with a few outliers in groups 4 and 5. Groups 4 and 5 are the tracts in
large counties. Statistically significant differences are indicated by
an "X" on these scatter plots.

Figure D-6 displays the tract-level summary vacant housing unit item
allocation rate differences, by tract group. The differences for the
five groups are centered on zero. Statistically significant differences
are indicated by an "X" on these scatter plots.

Figure D-7 displays the tract-level summary population and occupied
housing unit item allocation rate differences, by tract group. It shows
that for each group, for a majority of the summary population and
occupied housing unit item allocation rates, the ACS 3-year averages are
lower than the Census 2000 sample estimates. For groups 1, 2, and 3 the
majority of the differences are between --10 and 0. For groups 4 and 5,
a majority of the differences are between --20 and 0. Statistically
significant differences are indicated by an "X" on these scatter plots.

The results presented in Table 11, Table 12, and Appendix D show that
the ACS had fewer allocations than the census for occupied housing unit
and population items. This could be a sign of potentially higher item
nonresponse error for census occupied housing unit and population item
estimates. Since the census did not have a content edit to followup on
missing or incomplete items on a mail returned questionnaire, and the
ACS does have a content edit, these results are not unexpected.

**3.4 Sample Completeness Rates**

We calculated sample completeness rates to measure how well the ACS and
Census 2000 sample represent their target area's population or housing.
The rates are 100 times the ratio of the survey's estimate of population
or housing units to the target area's count of population or housing
units. For both the ACS and Census 2000 sample completeness rates, the
100 percent Census 2000 counts were used for the target area's
population and housing unit counts. We computed these rates for each of
the 36 ACS counties. They cannot be computed at the tract level because
the final housing and population controls are used in the denominator of
the ACS rates. We compute a housing unit completeness rate, and a
household population completeness rate. The county-level comparison
results are presented in section 3.4.1.

These rates measure nonresponse and coverage errors. Survey nonresponse
and undercoverage can introduce bias if they result in certain groups of
people or units with specific characteristics being excluded from the
sample estimates. Survey overcoverage can result in bias if those
included in the survey more than once share specific characteristics to
a higher degree than those included in the survey only once. Since the
completeness rates are 100 times the ratio of the survey's estimate to
the target area's count, a rate of 100 is desired. A rate greater than
100 represents overcoverage of the target area by the survey, and a rate
less than 100 represents undercoverage of the target area by the survey.

The Census 2000 sample completeness rates are 100 times the ratio of the
Census 2000 weighted count of long form sample data defined housing
units or their residents to the 100 percent Census 2000 total housing
unit or household population count. The numerator of these rates are
weighted by the reciprocal of the sampling fraction used to designate
long form sample units for the block in which they were enumerated. This
weight is equal to 2, 4, 6 or 8. The denominators of these rates are the
100 percent Census 2000 housing units or household population counts,
which are constants, so they are not weighted.

The ACS three-year average sample completeness rates are 100 times the
ratio of the ACS total housing units or household population weighted by
their probability of selection (base weight) to the ACS final housing
and population controls. Census data are used for the final housing and
population controls, so the denominators of these rates are constants.

The sample completeness rate formulae are below.

The Census 2000 Sample Completeness Rates are:

-   Housing unit = (Census 2000 weighted count of long form sample data
    defined housing units / Census 2000 total housing units) × 100

-   Household population = (Census 2000 weighted count of long form
    household population in sample data defined housing units / Census
    2000 total household population) × 100

    The ACS three-year Average Sample Completeness Rates are:

```{=html}
<!-- -->
```
-   Housing unit = (ACS base weighted total housing units / ACS final
    total housing units) × 100

-   Household population = (ACS base weighted household population / ACS
    final household population) × 100

*Number range CHAPTER3.4.1 County Comparisons*

This section contains the county level sample completeness comparison
results. In this section we compare the ACS three-year average and
Census 2000 housing unit sample completeness rates and the household
population sample completeness rates. We first compare the differences
for each of the 36 counties, and then compare the differences when the
values are averaged across all the counties.

Table 13 shows the number of counties with statistically significantly
different ACS three-year average and Census 2000 sample completeness
rates. Table 14 shows the results of comparing the average of the 36
county housing unit sample completeness rates and household population
sample completeness rates.

  ---------------------------------------------------------------------------------
  **Table 13. Number of Counties                                    
  with Statistically Significantly                                  
  Different Sample Completeness                                     
  Rates ^C^**                                                       
  --------------------------------- --------------- --------------- ---------------
  **Quality Measure**               **Number of 36  **Number of 36  **Number of 36
                                    Counties Not    Counties        Counties
                                    Statistically   Statistically   Statistically
                                    Significantly   Significantly   Significantly
                                    Different**     Different with  Different with
                                                    ACS \> Census** Census \> ACS**

  Housing unit sample completeness  11              21              4
  rate                                                              

  Household population sample       22              8               6
  completeness rate                                                 

  C -- Comparisons are based on a                                   
  non-random sample of counties                                     
  ---------------------------------------------------------------------------------

+----------------------------------+-------+-------+---------+--------+
| **Table 14. Comparison of Sample |       |       |         |        |
| Completeness Rates: ACS          |       |       |         |        |
| Three-year Averages and Census   |       |       |         |        |
| 2000 Sample Estimates, County    |       |       |         |        |
| Averages**                       |       |       |         |        |
+==================================+=======+=======+=========+========+
| **Quality Measure**              | **ACS | **C   | *       | **     |
|                                  | Aver  | ensus | *Differ | Margin |
|                                  | age** | Aver  | ence^D^ | of     |
|                                  |       | age** | of      | Erro   |
|                                  |       |       | Ave     | r^C^** |
|                                  |       |       | rages** |        |
+----------------------------------+-------+-------+---------+--------+
| Housing unit sample completeness | 92.9  | 90.3  | 2.6     | ± 2.1  |
| rate                             |       |       |         |        |
+----------------------------------+-------+-------+---------+--------+
| Household population sample      | 90.4  | 91.1  | -0.7    | ^NS^ ± |
| completeness rate                |       |       |         | 2.1    |
+----------------------------------+-------+-------+---------+--------+
| D -- The difference is the ACS   |       |       |         |        |
| average minus the Census 2000    |       |       |         |        |
| average.                         |       |       |         |        |
|                                  |       |       |         |        |
| C -- This comparison is based on |       |       |         |        |
| a non-random sample of counties  |       |       |         |        |
|                                  |       |       |         |        |
| NS -- the ACS and Census         |       |       |         |        |
| averages are not statistically   |       |       |         |        |
| significantly different for this |       |       |         |        |
| quality measure.                 |       |       |         |        |
+----------------------------------+-------+-------+---------+--------+

Table 13, Table 14, and Table A-1 together show that the ACS sample
represents more of its target housing unit population than does the
census sample. Table 13 shows that 25 out of the 36 county housing unit
sample completeness rates were statistically significantly different.
For 21 counties with statistically significantly different housing unit
sample completeness rates, the ACS three-year average housing unit
sample completeness rate was larger and, as shown in Table A-1, closer
to one than the Census 2000 sample estimate. Table A-1 in Appendix A
contains the ACS three-year average and Census 2000 housing unit sample
completeness rates (HCR) for each of the 36 counties. The counties whose
differences are not statistically significant are marked with an "NS" in
the table. Table A-1 also shows that the 21 statistically significantly
larger ACS housing unit sample completeness rates are closer to one than
the census rates, and the four statistically significantly larger census
housing unit sample completeness rates are closer to one than the ACS
rates. The housing unit sample completeness rates are all less than one
except for the ACS rate for two counties. Table 14 shows that, on
average, the housing unit sample completeness rate for the ACS
three-year average was larger and closer to one than the Census 2000
sample estimate by 2.6. Since the margin of error for the difference is
only 2.1 percent, the resulting confidence interval would not contain
zero. So, the average difference is statistically significant.

Figures C-7 and C-8 in Appendix C display the housing unit sample
completeness rate and household population sample completeness rate
differences, respectively, for all 36 counties through the use of
one-dimensional scatter plots. For these plots, differences between the
ACS three-year averages and the Census 2000 sample quality measures are
located on the vertical axis; counties are on the horizontal axis. We
sorted counties by their 100 percent count of census housing units. The
sorts were in ascending order, from left to right. For example, the
difference for the county with the smallest count is the left-most point
in the plots, while the difference for the county with the largest count
is the right-most point. We used a "jittering" process so that we could
plot the differences in this way. The "jittering" process assigned a
unique integer to each county so as to achieve this sort, where the
county with the smallest count received the smallest integer, etc.

Figure C-7 shows that the majority of counties have larger ACS housing
unit sample completeness rates than census sample completeness rates. In
addition, for the counties with the largest number of census housing
units, the ACS housing unit sample completeness rates are statistically
significantly larger than the census housing unit sample completeness
rates. Statistically significant differences are identified by an "X" on
these plots.

Table 13, Table 14, and Table A-1 also show that the ACS sample and
census sample represent their target area's household population about
equally well. Table 13 shows that 14 out of the 36 county sample
completeness rates for household population were statistically
significantly different. For eight counties with significantly different
household population sample completeness rates, the ACS three-year
average was larger and as shown in Table A-1 closer to one than the
Census 2000 sample estimate. Table A-1 in Appendix A contains the ACS
three-year average and Census 2000 household population sample
completeness rates for each of the 36 counties. The counties whose
differences are not statistically significant are marked with an "NS" in
the table. Table A-1 also shows that the eight statistically
significantly larger ACS sample completeness rates for household
population (PCR) are closer to one than the census rates, and the six
statistically significantly larger census sample completeness rates for
household population are closer to one than the ACS rates. The household
population sample completeness rates are all less than one except for
the ACS rate for one county. Table 14 shows that the average household
population sample completeness rates were not statistically
significantly different.

Figure C-8 shows that the household population sample completeness rate
differences are spread nearly evenly about zero. In addition, as the
number of census housing units in the county increases, the differences
seem to get smaller. Statistically significant differences are
identified by an "X" on these plots.

The results presented in Table 13, Table 14, Appendix A, Figure C-7, and
Figure C-8, show that, in general, the ACS had housing unit sample
completeness rates slightly closer to one than the census sample, but
their household population sample completeness rates were about equally
close to one. The sample completeness rates measure nonresponse error
and coverage error, and a rate of one is optimal. So, the difference in
the housing unit sample completeness rates could signal that the census
has somewhat more of these errors.

**4. CONCLUSIONS**

We observed overall significant differences between the quality measures
for the ACS three-year averages and the Census 2000 sample estimates.
The results show that the census had more respondents mailback their
questionnaires (the census had a generally higher self-response rate)
while the ACS obtained more information from respondents during followup
operations (respondents in follow-up operations included households who
did not mailback their forms or who returned their forms via mail but
left some items blank). As a whole, a higher proportion of households
responded in the ACS (the ACS had a generally lower nonresponse rate).
The ACS tended to obtain more information (lower item allocation rates)
on sample housing units than the census, with one exception: the census
tended to obtain more information on vacant housing units. The ACS
exhibited better coverage of its target area's housing units than did
the census (the ACS had housing unit sample completeness rates closer to
100 than did the census), but the two surveys covered their target
area's population about equally well (the two surveys' population sample
completeness ratios were comparable). These results seem to be explained
by the operational and methodological differences between the ACS and
the census.

We observed the overall significant differences at the county level,
also. For the self-response rate, most of the counties had statistically
significantly higher Census 2000 long form rates - this indicated that
the census performed better than the ACS with respect to this quality
measure. However, for the sample unit nonresponse and summary item
allocation rates, a majority (if not all) of the counties had
statistically significantly lower ACS three-year average rates - this
indicated that the ACS performed better than the census for these
quality measures. For the sample completeness rates, the number of
counties with statistically significant differences and the number of
counties without statistically significant differences is about even.

For the most part, we observed the same significant differences above at
the tract level. The census seemed to collect more forms through the
mail in tracts for all five tract groups. On average, the census
collected more information on vacant housing units in tracts in medium
counties (tract groups 2, 3) and large counties with tract populations
greater than 4,000 persons (tract group 5). The ACS, on the other hand,
obtained more information for units that did not respond through the
mail for tracts in all five tract groups. The ACS also tended to obtain
more information for units in tracts in all five tract groups, as well.

These quality measures suggest that the ACS multi-year averages are at
least as good as the estimates from the long form. When we also consider
the enhanced timeliness of information from the ACS, the superiority of
reengineering the 2010 Census over retaining traditional methods is
clear. In addition, while further study is needed, it appears that the
permanent, on-going nature of the ACS program contributes to lower ACS
nonresponse rates, and hence less chance for nonresponse error and bias
in the estimates.

**5. REFERENCES**

Asiala, Mark and Dawn Haines, *Census 2000 long Form -- Data Groupings
for Generalized Design Factors*, DSSD CENSUS PROCEDURES AND OPERATIONS
MEMORANDUM SERIES #LL-11, Bureau of the Census, September 16, 2002.

Bench, Katie, *Census 2000 Sample Data and ACS three-year Averages
Quality Measures Comparison Documentation*, Bureau of the Census, May
23, 2003.

Bureau of the Census, *Summary File 3 Technical Documentation, 2000
Census of Population and Housing*,
<http://www.census.gov/prod/cen2000/doc/sf3.pdf>, February 2003.

Bureau of the Census, *American Community Survey Operational Plan*,
Release 1, March 2003.

Bureau of the Census, *Meeting 21^st^ Century Demographic Data
Needs---Implementing American Community Survey*, Report1: Demonstrating
Operational Feasibility, July 2001.

Bureau of the Census, *Census 2000 Operational Plan*,
<http://www.census.gov/dmd/www/pdf/Operational2000.pdf>, December 2000.

**Appendix A**

######### County Level Quality Measures

<table style="width:100%;">
<colgroup>
<col style="width: 20%" />
<col style="width: 6%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 8%" />
</colgroup>
<thead>
<tr class="header">
<th colspan="11"><h1
id="table-a-1.-comparison-of-self-response-rates-sample-unit-nonresponse-rates-and-sample-completeness-rates-acs-three-year-averages-and-census-2000-long-form-sample-estimates-by-county">Table
A-1. Comparison of Self-response Rates, Sample Unit Nonresponse Rates,
and Sample Completeness Rates: ACS Three-year Averages and Census 2000
Long Form Sample Estimates, by County</h1></th>
</tr>
<tr class="odd">
<th><strong>County</strong></th>
<th><strong>ACS SRR<sup>1</sup></strong></th>
<th><strong>Census SRR<sup>1</sup></strong></th>
<th><strong>ACS UNR<sup>2</sup></strong></th>
<th><strong>Census UNR<sup>2</sup></strong></th>
<th><strong>ACS OUNR<sup>3</sup></strong></th>
<th><strong>Census OUNR<sup>3</sup></strong></th>
<th><strong>ACS HCR<sup>4</sup></strong></th>
<th><strong>Census HCR<sup>4</sup></strong></th>
<th><strong>ACS PCR<sup>5</sup></strong></th>
<th><strong>Census PCR<sup>5</sup></strong></th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td>Pima County, AZ</td>
<td>62.1</td>
<td>69.7</td>
<td>5.7</td>
<td>11.7</td>
<td>6.3</td>
<td>11.4</td>
<td>94.7</td>
<td>88.3</td>
<td>91.0</td>
<td>88.5</td>
</tr>
<tr class="even">
<td>Jefferson County, AR</td>
<td>50.6</td>
<td>67.6</td>
<td>4.4</td>
<td>17.1</td>
<td>5.0</td>
<td>14.3</td>
<td>93.5</td>
<td>82.9</td>
<td><sup>NS</sup> 88.1</td>
<td><sup>NS</sup> 84.9</td>
</tr>
<tr class="odd">
<td>San Francisco County, CA</td>
<td>57.9</td>
<td>65.7</td>
<td>6.0</td>
<td>12.4</td>
<td>6.4</td>
<td>12.0</td>
<td>92.9</td>
<td>87.6</td>
<td><sup>NS</sup> 88.3</td>
<td><sup>NS</sup> 88.0</td>
</tr>
<tr class="even">
<td>Tulare County, CA</td>
<td>50.1</td>
<td>63.4</td>
<td>3.6</td>
<td>11.4</td>
<td>3.9</td>
<td>10.1</td>
<td>94.5</td>
<td>88.7</td>
<td><sup>NS</sup> 88.4</td>
<td><sup>NS</sup> 89.4</td>
</tr>
<tr class="odd">
<td>Broward County, FL</td>
<td>56.4</td>
<td>60.9</td>
<td>3.9</td>
<td>9.5</td>
<td>4.5</td>
<td>11.7</td>
<td>97.8</td>
<td>90.5</td>
<td>92.9</td>
<td>88.6</td>
</tr>
<tr class="even">
<td>Upson County, GA</td>
<td>56.0</td>
<td>69.7</td>
<td>3.2</td>
<td>8.9</td>
<td>3.5</td>
<td>7.1</td>
<td><sup>NS</sup> 95.9</td>
<td><sup>NS</sup> 91.1</td>
<td><sup>NS</sup> 89.8</td>
<td><sup>NS</sup> 92.5</td>
</tr>
<tr class="odd">
<td>Lake County, IL</td>
<td>65.3</td>
<td>72.0</td>
<td>3.9</td>
<td>6.8</td>
<td>4.1</td>
<td>6.4</td>
<td>98.1</td>
<td>93.2</td>
<td><sup>NS</sup> 94.0</td>
<td><sup>NS</sup> 93.8</td>
</tr>
<tr class="even">
<td>Miami County, IN</td>
<td>59.8</td>
<td>70.6</td>
<td>4.3</td>
<td>21.4</td>
<td>4.8</td>
<td>17.1</td>
<td>95.4</td>
<td>78.6</td>
<td>96.2</td>
<td>81.9</td>
</tr>
<tr class="odd">
<td>Black Hawk County, IA</td>
<td>69.6</td>
<td>76.6</td>
<td>3.5</td>
<td>9.4</td>
<td>3.7</td>
<td>7.9</td>
<td>96.4</td>
<td>90.6</td>
<td><sup>NS</sup> 93.5</td>
<td><sup>NS</sup> 92.9</td>
</tr>
<tr class="even">
<td>De Soto Parish, LA</td>
<td>49.3</td>
<td>62.8</td>
<td><sup>NS</sup> 6.5</td>
<td><sup>NS</sup> 6.7</td>
<td><sup>NS</sup> 7.5</td>
<td><sup>NS</sup> 7.8</td>
<td><sup>NS</sup> 87.1</td>
<td><sup>NS</sup> 93.3</td>
<td>83.1</td>
<td>94.9</td>
</tr>
<tr class="odd">
<td>Calvert County, MD</td>
<td>63.0</td>
<td>71.5</td>
<td>2.9</td>
<td>5.2</td>
<td>3.2</td>
<td>4.8</td>
<td><sup>NS</sup> 93.2</td>
<td><sup>NS</sup> 94.8</td>
<td><sup>NS</sup> 91.6</td>
<td><sup>NS</sup> 95.2</td>
</tr>
<tr class="even">
<td>Hampden County, MA</td>
<td>61.9</td>
<td>69.1</td>
<td>5.0</td>
<td>11.3</td>
<td>5.4</td>
<td>10.0</td>
<td>96.0</td>
<td>88.7</td>
<td>92.8</td>
<td>90.1</td>
</tr>
<tr class="odd">
<td>Madison County, MS</td>
<td>54.5</td>
<td>71.6</td>
<td>4.3</td>
<td>12.5</td>
<td>4.7</td>
<td>11.3</td>
<td>95.4</td>
<td>87.5</td>
<td><sup>NS</sup> 90.4</td>
<td><sup>NS</sup> 89.7</td>
</tr>
<tr class="even">
<td>Iron County, MO</td>
<td>48.4</td>
<td>70.2</td>
<td><sup>NS</sup> 3.8</td>
<td><sup>NS</sup> 4.4</td>
<td><sup>NS</sup> 4.6</td>
<td><sup>NS</sup> 4.5</td>
<td><sup>NS</sup> 93.0</td>
<td><sup>NS</sup> 95.6</td>
<td><sup>NS</sup> 91.2</td>
<td><sup>NS</sup> 96.5</td>
</tr>
<tr class="odd">
<td>Reynolds County, MO</td>
<td>38.2</td>
<td>71.9</td>
<td><sup>NS</sup> 2.9</td>
<td><sup>NS</sup> 1.4</td>
<td><sup>NS</sup> 4.1</td>
<td><sup>NS</sup> 2.6</td>
<td><sup>NS</sup> 91.8</td>
<td><sup>NS</sup> 98.6</td>
<td><sup>NS</sup> 86.6</td>
<td><sup>NS</sup> 98.1</td>
</tr>
<tr class="even">
<td>Washington County, MO</td>
<td>40.8</td>
<td>66.1</td>
<td>4.4</td>
<td>1.8</td>
<td>5.3</td>
<td>1.3</td>
<td>88.6</td>
<td>98.2</td>
<td>84.0</td>
<td>98.6</td>
</tr>
<tr class="odd">
<td>Flathead County, MT</td>
<td>60.1</td>
<td>72.9</td>
<td><sup>NS</sup> 3.8</td>
<td><sup>NS</sup> 3.7</td>
<td><sup>NS</sup> 4.4</td>
<td><sup>NS</sup> 4.4</td>
<td><sup>NS</sup> 94.8</td>
<td><sup>NS</sup> 96.3</td>
<td><sup>NS</sup> 93.7</td>
<td><sup>NS</sup> 95.1</td>
</tr>
<tr class="even">
<td>Lake County, MT</td>
<td>52.4</td>
<td>74.6</td>
<td>6.0</td>
<td>12.2</td>
<td><sup>NS</sup> 7.7</td>
<td><sup>NS</sup> 9.2</td>
<td><sup>NS</sup> 89.5</td>
<td><sup>NS</sup> 87.8</td>
<td><sup>NS</sup> 87.5</td>
<td><sup>NS</sup> 88.5</td>
</tr>
<tr class="odd">
<td>Douglas County, NE</td>
<td>67.2</td>
<td>72.5</td>
<td>3.9</td>
<td>6.6</td>
<td>4.2</td>
<td>5.9</td>
<td>95.5</td>
<td>93.4</td>
<td><sup>NS</sup> 93.8</td>
<td><sup>NS</sup> 93.7</td>
</tr>
<tr class="even">
<td>Otero County, NM</td>
<td>59.3</td>
<td>65.0</td>
<td>4.8</td>
<td>7.2</td>
<td>6.0</td>
<td>9.8</td>
<td>85.3</td>
<td>92.8</td>
<td>82.9</td>
<td>89.5</td>
</tr>
<tr class="odd">
<td>Bronx Borough, NY</td>
<td>36.0</td>
<td>52.9</td>
<td>9.7</td>
<td>22.2</td>
<td>10.5</td>
<td>21.0</td>
<td>92.0</td>
<td>77.8</td>
<td>83.4</td>
<td>79.8</td>
</tr>
<tr class="even">
<td>Rockland County, NY</td>
<td>57.6</td>
<td>65.3</td>
<td>3.5</td>
<td>5.5</td>
<td>3.6</td>
<td>5.2</td>
<td>01.2</td>
<td>94.5</td>
<td><sup>NS</sup> 97.1</td>
<td><sup>NS</sup> 94.6</td>
</tr>
<tr class="odd">
<td>Franklin County, OH</td>
<td>64.2</td>
<td>69.3</td>
<td>1.9</td>
<td>5.8</td>
<td>2.1</td>
<td>5.9</td>
<td>97.6</td>
<td>94.2</td>
<td><sup>NS</sup> 94.6</td>
<td><sup>NS</sup> 94.2</td>
</tr>
<tr class="even">
<td>Multnomah County, OR</td>
<td>65.0</td>
<td>70.4</td>
<td>3.6</td>
<td>5.0</td>
<td>3.8</td>
<td>5.1</td>
<td>96.3</td>
<td>95.0</td>
<td><sup>NS</sup> 93.9</td>
<td><sup>NS</sup> 94.4</td>
</tr>
<tr class="odd">
<td>Fulton County, PA</td>
<td>57.4</td>
<td>75.0</td>
<td><sup>NS</sup> 3.9</td>
<td><sup>NS</sup> 4.6</td>
<td><sup>NS</sup> 4.7</td>
<td><sup>NS</sup> 4.8</td>
<td><sup>NS</sup> 94.0</td>
<td><sup>NS</sup> 95.4</td>
<td><sup>NS</sup> 94.9</td>
<td><sup>NS</sup> 94.4</td>
</tr>
<tr class="even">
<td>Schuylkill County, PA</td>
<td>69.5</td>
<td>77.3</td>
<td>3.8</td>
<td>5.6</td>
<td><sup>NS</sup> 4.3</td>
<td><sup>NS</sup> 5.3</td>
<td><sup>NS</sup> 95.0</td>
<td><sup>NS</sup> 94.4</td>
<td><sup>NS</sup> 93.7</td>
<td><sup>NS</sup> 95.6</td>
</tr>
<tr class="odd">
<td>Sevier County, TN</td>
<td>58.7</td>
<td>65.2</td>
<td><sup>NS</sup> 4.9</td>
<td><sup>NS</sup> 6.2</td>
<td><sup>NS</sup> 5.9</td>
<td><sup>NS</sup> 5.6</td>
<td>83.4</td>
<td>93.8</td>
<td>88.2</td>
<td>94.1</td>
</tr>
<tr class="even">
<td>Fort Bend County, TX</td>
<td><sup>NS</sup> 56.7</td>
<td><sup>NS</sup> 66.9</td>
<td><sup>NS</sup> 4.8</td>
<td><sup>NS</sup> 6.1</td>
<td><sup>NS</sup> 5.0</td>
<td><sup>NS</sup> 6.2</td>
<td><sup>NS</sup> 90.6</td>
<td><sup>NS</sup> 93.9</td>
<td>84.4</td>
<td>93.4</td>
</tr>
<tr class="odd">
<td>Harris County, TX</td>
<td>47.9</td>
<td>60.6</td>
<td><sup>NS</sup> 4.2</td>
<td><sup>NS</sup> 10.1</td>
<td><sup>NS</sup> 4.6</td>
<td><sup>NS</sup> 10.2</td>
<td>94.6</td>
<td>89.9</td>
<td><sup>NS</sup> 90.7</td>
<td><sup>NS</sup> 90.1</td>
</tr>
<tr class="even">
<td>Starr County, TX</td>
<td>21.7</td>
<td>54.0</td>
<td>6.0</td>
<td>11.9</td>
<td><sup>NS</sup> 7.4</td>
<td><sup>NS</sup> 10.1</td>
<td><sup>NS</sup> 86.9</td>
<td><sup>NS</sup> 88.1</td>
<td>78.5</td>
<td>90.6</td>
</tr>
<tr class="odd">
<td>Zapata County, TX</td>
<td>25.7</td>
<td>62.5</td>
<td>6.8</td>
<td>13.0</td>
<td><sup>NS</sup> 10.0</td>
<td><sup>NS</sup> 11.6</td>
<td>74.4</td>
<td>87.0</td>
<td><sup>NS</sup> 73.6</td>
<td><sup>NS</sup> 86.9</td>
</tr>
<tr class="even">
<td>Petersburg City, VA</td>
<td>52.1</td>
<td>62.8</td>
<td>2.4</td>
<td>19.1</td>
<td>2.9</td>
<td>13.8</td>
<td>99.1</td>
<td>80.9</td>
<td>92.1</td>
<td>82.9</td>
</tr>
<tr class="odd">
<td>Yakima County, WA</td>
<td>58.4</td>
<td>65.8</td>
<td>3.7</td>
<td>10.6</td>
<td>3.9</td>
<td>9.5</td>
<td>94.4</td>
<td>89.4</td>
<td><sup>NS</sup> 89.2</td>
<td><sup>NS</sup> 88.9</td>
</tr>
<tr class="even">
<td>Ohio County, WV</td>
<td><sup>NS</sup> 69.1</td>
<td><sup>NS</sup> 72.6</td>
<td><sup>NS</sup> 3.4</td>
<td><sup>NS</sup> 4.7</td>
<td><sup>NS</sup> 3.8</td>
<td><sup>NS</sup> 3.9</td>
<td>00.2</td>
<td>95.3</td>
<td><sup>NS</sup> 99.5</td>
<td><sup>NS</sup> 96.5</td>
</tr>
<tr class="odd">
<td>Oneida County, WI</td>
<td><sup>NS</sup> 71.6</td>
<td><sup>NS</sup> 78.0</td>
<td>3.9</td>
<td>19.3</td>
<td>5.9</td>
<td>12.2</td>
<td>87.3</td>
<td>80.7</td>
<td>96.1</td>
<td>87.4</td>
</tr>
<tr class="even">
<td>Vilas County, WI</td>
<td><sup>R</sup> 56.6</td>
<td></td>
<td>5.5</td>
<td>18.4</td>
<td>10.7</td>
<td>14.2</td>
<td>87.3</td>
<td>81.6</td>
<td>06.5</td>
<td>86.4</td>
</tr>
<tr class="odd">
<td colspan="11">1 – SRR = Self-response rate</td>
</tr>
<tr class="even">
<td colspan="11">2 – UNR = sample unit nonresponse rate</td>
</tr>
<tr class="odd">
<td colspan="11">3 – OUNR = occupied sample unit nonresponse rate</td>
</tr>
<tr class="even">
<td colspan="11">4 – HCR = Housing unit sample completeness rate</td>
</tr>
<tr class="odd">
<td colspan="11">5 – PCR = Household population sample completeness
rate</td>
</tr>
<tr class="even">
<td colspan="11">NS – The ACS three-year average and Census 2000 sample
quality measure are not statistically significantly different for this
county.</td>
</tr>
<tr class="odd">
<td colspan="11">R – This county was removed from the county comparison
for this quality measure because the Census 2000 sample quality measure
was undefined.</td>
</tr>
</tbody>
</table>

+------------------+-----+------+--------+--------+---------+---------+
| # Table A-2.     |     |      |        |        |         |         |
| Comparison of Su |     |      |        |        |         |         |
| mmary Allocation |     |      |        |        |         |         |
|  Rates for Popul |     |      |        |        |         |         |
| ation Items: ACS |     |      |        |        |         |         |
|  Three-year Aver |     |      |        |        |         |         |
| ages and Census  |     |      |        |        |         |         |
| 2000 Sample Esti |     |      |        |        |         |         |
| mates, by County |     |      |        |        |         |         |
+==================+=====+======+========+========+=========+=========+
| **County**       | *   | **Ce | **ACS  | **     | **ACS   | *       |
|                  | *AC | nsus | Sel    | Census | I       | *Census |
|                  | S** | Tot  | f-resp | Sel    | ntervie | I       |
|                  |     | al** | onse** | f-resp | wer-res | ntervie |
|                  | **T |      |        | onse** | ponse** | wer-res |
|                  | ota |      |        |        |         | ponse** |
|                  | l** |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Pima County, AZ  | 6.2 | 9.9  | 7.5    | 8.4    | 4.5     | 13.8    |
+------------------+-----+------+--------+--------+---------+---------+
| Jefferson        | 7.4 | 13.8 | ^NS^   | ^NS^   | 3.5     | 20.1    |
| County, AR       |     |      | 11.4   | 11.6   |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| San Francisco    | 7.5 | 12.3 | 8.8    | 10.3   | 6.0     | 17.6    |
| County, CA       |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Tulare County,   | 7.1 | 13.2 | 9.8    | 12.0   | 4.9     | 15.7    |
| CA               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Broward County,  | 6.9 | 11.1 | 8.7    | 9.8    | 5.1     | 13.2    |
| FL               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Upson County, GA | 8.1 | 11.7 | ^NS^   | ^NS^   | 4.7     | 11.0    |
|                  |     |      | 11.1   | 12.3   |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Lake County, IL  | 6.1 | 10.3 | 7.1    | 8.5    | 4.8     | 15.3    |
+------------------+-----+------+--------+--------+---------+---------+
| Miami County, IN | 5.9 | 12.9 | 7.9    | 10.8   | 3.2     | 23.7    |
+------------------+-----+------+--------+--------+---------+---------+
| Black Hawk       | 6.0 | 9.6  | ^NS^   | ^NS^   | 3.9     | 15.8    |
| County, IA       |     |      | 7.5    | 8.0    |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| De Soto Parish,  | 7.6 | 13.0 | ^NS^   | ^NS^   | 3.0     | 11.5    |
| LA               |     |      | 12.1   | 13.6   |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Calvert County,  | 5.4 | 8.9  | 6.6    | 8.2    | 3.6     | 11.2    |
| MD               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Hampden County,  | 6.7 | 11.7 | 8.4    | 10.6   | 4.3     | 14.6    |
| MA               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Madison County,  | 6.0 | 13.0 | 8.0    | 10.0   | 3.9     | 25.9    |
| MS               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Iron County, MO  | 6.9 | 11.8 | ^NS^   | ^NS^   | 3.7     | 13.5    |
|                  |     |      | 11.0   | 11.0   |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Reynolds County, | 6.1 | 13.6 | ^NS^   | ^NS^   | 3.7     | 16.7    |
| MO               |     |      | 11.3   | 12.8   |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Washington       | 6.4 | 12.0 | ^NS^   | ^NS^   | 3.5     | 13.7    |
| County, MO       |     |      | 10.3   | 11.2   |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Flathead County, | 6.8 | 11.6 | ^NS^   | ^NS^   | 3.9     | 17.9    |
| MT               |     |      | 9.0    | 9.5    |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Lake County, MT  | 6.3 | 7.6  | ^NS^   | ^NS^   | ^NS^    | ^NS^    |
|                  |     |      | 7.7    | 8.1    | 4.8     | 7.5     |
+------------------+-----+------+--------+--------+---------+---------+
| Douglas County,  | 5.6 | 9.3  | ^NS^   | ^NS^   | 3.2     | 14.8    |
| NE               |     |      | 7.2    | 7.6    |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Otero County, NM | 6.2 | 9.5  | ^NS^   | ^NS^   | 3.1     | 12.8    |
|                  |     |      | 8.4    | 7.9    |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Bronx Borough,   | 8.5 | 16.3 | 13.7   | 15.8   | 5.5     | 17.4    |
| NY               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Rockland County, | 6.8 | 10.8 | 8.1    | 9.7    | 5.3     | 13.1    |
| NY               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Franklin County, | 5.0 | 9.4  | 6.3    | 7.5    | 3.2     | 14.2    |
| OH               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Multnomah        | 6.0 | 9.2  | 7.0    | 7.7    | 4.9     | 13.0    |
| County, OR       |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Fulton County,   | ^   | ^NS^ | ^NS^   | ^NS^   | ^NS^    | ^NS^    |
| PA               | NS^ | 10.2 | 9.6    | 9.9    | 5.0     | 11.7    |
|                  | 7.6 |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Schuylkill       | 5.9 | 10.0 | 7.1    | 8.9    | 3.2     | 14.2    |
| County, PA       |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Sevier County,   | 6.7 | 11.1 | ^NS^   | ^NS^   | 3.9     | 14.2    |
| TN               |     |      | 8.8    | 9.5    |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Fort Bend        | 5.7 | 10.8 | 7.1    | 9.2    | 4.1     | 14.6    |
| County, TX       |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Harris County,   | 6.2 | 12.1 | 8.6    | 11.3   | 4.3     | 13.7    |
| TX               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Starr County, TX | 3.9 | 9.1  | ^NS^   | ^NS^   | 1.7     | 8.1     |
|                  |     |      | 12.5   | 12.1   |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Zapata County,   | 4.2 | 13.8 | 8.8    | 17.3   | 2.8     | 7.6     |
| TX               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Petersburg City, | 7.3 | 13.9 | 11.5   | 13.7   | 3.2     | 14.6    |
| VA               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Yakima County,   | 7.6 | 10.7 | 8.9    | 10.5   | 6.6     | 11.1    |
| WA               |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Ohio County, WV  | 7.6 | 10.3 | ^NS^   | ^NS^   | 6.3     | 12.3    |
|                  |     |      | 8.1    | 9.5    |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Oneida County,   | ^   | ^NS^ | ^NS^   | ^NS^   | ^NS^    | ^NS^    |
| WI               | NS^ | 8.4  | 8.0    | 8.7    | 3.3     | 8.2     |
|                  | 6.6 |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| Vilas County, WI | 6.5 | 10.5 | ^NS^   | ^NS^   | 4.9     | 10.5    |
|                  |     |      | 7.8    | 5.1    |         |         |
+------------------+-----+------+--------+--------+---------+---------+
| NS -- The ACS    |     |      |        |        |         |         |
| three-year       |     |      |        |        |         |         |
| average and      |     |      |        |        |         |         |
| Census 2000      |     |      |        |        |         |         |
| sample quality   |     |      |        |        |         |         |
| measure are not  |     |      |        |        |         |         |
| statistically    |     |      |        |        |         |         |
| significantly    |     |      |        |        |         |         |
| different for    |     |      |        |        |         |         |
| this county.     |     |      |        |        |         |         |
+------------------+-----+------+--------+--------+---------+---------+

<table>
<colgroup>
<col style="width: 22%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 9%" />
<col style="width: 9%" />
<col style="width: 11%" />
<col style="width: 12%" />
<col style="width: 1%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 1%" />
</colgroup>
<thead>
<tr class="header">
<th colspan="10"><h1
id="table-a-3.-comparison-of-summary-allocation-rates-for-housing-units-items-acs-three-year-averages-and-census-2000-sample-estimates-by-county">Table
A-3. Comparison of Summary Allocation Rates for Housing Units Items: ACS
Three-year Averages and Census 2000 Sample Estimates, by
County</h1></th>
<th></th>
</tr>
<tr class="odd">
<th></th>
<th colspan="6"><strong>Occupied Housing Unit Items</strong></th>
<th></th>
<th colspan="2"><strong>Vacant Housing Unit Items</strong></th>
<th></th>
</tr>
<tr class="header">
<th><strong>County</strong></th>
<th><p><strong>ACS</strong></p>
<p><strong>Total</strong></p></th>
<th><strong>Census Total</strong></th>
<th><strong>ACS Self-response</strong></th>
<th><strong>Census Self-response</strong></th>
<th><strong>ACS Interviewer-response</strong></th>
<th><strong>Census Interviewer-response</strong></th>
<th></th>
<th><strong>ACS Total</strong></th>
<th><strong>Census Total</strong></th>
<th></th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td>Pima County, AZ</td>
<td>7.4</td>
<td>13.5</td>
<td>6.9</td>
<td>12.3</td>
<td>9.0</td>
<td>18.1</td>
<td></td>
<td><sup>NS</sup> 14.7</td>
<td><sup>NS</sup> 14.4</td>
<td></td>
</tr>
<tr class="even">
<td>Jefferson County, AR</td>
<td>8.9</td>
<td>18.2</td>
<td>8.9</td>
<td>16.2</td>
<td>9.4</td>
<td>25.8</td>
<td></td>
<td><sup>NS</sup> 28.4</td>
<td><sup>NS</sup> 24.5</td>
<td></td>
</tr>
<tr class="odd">
<td>San Francisco County, CA</td>
<td>9.5</td>
<td>17.2</td>
<td>9.4</td>
<td>15.7</td>
<td>9.8</td>
<td>22.4</td>
<td></td>
<td><sup>NS</sup> 15.6</td>
<td><sup>NS</sup> 16.1</td>
<td></td>
</tr>
<tr class="even">
<td>Tulare County, CA</td>
<td>9.5</td>
<td>17.5</td>
<td>8.1</td>
<td>15.9</td>
<td>11.7</td>
<td>21.8</td>
<td></td>
<td>28.6</td>
<td>21.4</td>
<td></td>
</tr>
<tr class="odd">
<td>Broward County, FL</td>
<td>7.6</td>
<td>15.0</td>
<td>7.6</td>
<td>14.8</td>
<td>8.0</td>
<td>15.9</td>
<td></td>
<td><sup>NS</sup> 13.5</td>
<td><sup>NS</sup> 13.6</td>
<td></td>
</tr>
<tr class="even">
<td>Upson County, GA</td>
<td>7.1</td>
<td>16.4</td>
<td>7.4</td>
<td>17.0</td>
<td>6.8</td>
<td>15.0</td>
<td></td>
<td><sup>NS</sup> 12.7</td>
<td><sup>NS</sup> 20.7</td>
<td></td>
</tr>
<tr class="odd">
<td>Lake County, IL</td>
<td>6.6</td>
<td>13.7</td>
<td>6.4</td>
<td>12.0</td>
<td>7.4</td>
<td>19.7</td>
<td></td>
<td><sup>NS</sup> 16.8</td>
<td><sup>NS</sup> 14.5</td>
<td></td>
</tr>
<tr class="even">
<td>Miami County, IN</td>
<td>7.6</td>
<td>16.8</td>
<td>7.4</td>
<td>15.0</td>
<td>8.0</td>
<td>26.8</td>
<td></td>
<td><sup>NS</sup> 21.3</td>
<td><sup>NS</sup> 23.1</td>
<td></td>
</tr>
<tr class="odd">
<td>Black Hawk County, IA</td>
<td>7.3</td>
<td>13.5</td>
<td>6.6</td>
<td>12.2</td>
<td>9.9</td>
<td>20.3</td>
<td></td>
<td>32.0</td>
<td>21.5</td>
<td></td>
</tr>
<tr class="even">
<td>De Soto Parish, LA</td>
<td>10.0</td>
<td>19.3</td>
<td>9.6</td>
<td>19.1</td>
<td>10.7</td>
<td>20.9</td>
<td></td>
<td><sup>NS</sup> 24.8</td>
<td><sup>NS</sup> 16.5</td>
<td></td>
</tr>
<tr class="odd">
<td>Calvert County, MD</td>
<td>6.0</td>
<td>12.2</td>
<td>6.0</td>
<td>11.4</td>
<td>6.7</td>
<td>15.0</td>
<td></td>
<td><sup>NS</sup> 19.9</td>
<td><sup>NS</sup> 16.7</td>
<td></td>
</tr>
<tr class="even">
<td>Hampden County, MA</td>
<td>7.9</td>
<td>16.2</td>
<td>7.2</td>
<td>15.3</td>
<td>9.5</td>
<td>19.5</td>
<td></td>
<td><sup>NS</sup> 20.2</td>
<td><sup>NS</sup> 18.7</td>
<td></td>
</tr>
<tr class="odd">
<td>Madison County, MS</td>
<td>7.4</td>
<td>17.1</td>
<td>7.2</td>
<td>14.0</td>
<td>8.8</td>
<td>31.2</td>
<td></td>
<td><sup>NS</sup> 15.5</td>
<td><sup>NS</sup> 20.5</td>
<td></td>
</tr>
<tr class="even">
<td>Iron County, MO</td>
<td>7.6</td>
<td>16.0</td>
<td>7.0</td>
<td>15.4</td>
<td>8.6</td>
<td>17.1</td>
<td></td>
<td>34.8</td>
<td>12.9</td>
<td></td>
</tr>
<tr class="odd">
<td>Reynolds County, MO</td>
<td>9.2</td>
<td>19.2</td>
<td>9.0</td>
<td>18.8</td>
<td>10.2</td>
<td>21.5</td>
<td></td>
<td><sup>NS</sup> 21.0</td>
<td><sup>NS</sup> 26.0</td>
<td></td>
</tr>
<tr class="even">
<td>Washington County, MO</td>
<td>7.2</td>
<td>17.3</td>
<td>6.5</td>
<td>17.4</td>
<td>8.0</td>
<td>17.8</td>
<td></td>
<td>40.2</td>
<td>21.8</td>
<td></td>
</tr>
<tr class="odd">
<td>Flathead County, MT</td>
<td>6.9</td>
<td>14.9</td>
<td>7.4</td>
<td>13.2</td>
<td>6.6</td>
<td>20.5</td>
<td></td>
<td><sup>NS</sup> 16.1</td>
<td><sup>NS</sup> 14.4</td>
<td></td>
</tr>
<tr class="even">
<td>Lake County, MT</td>
<td>7.2</td>
<td>11.4</td>
<td>6.3</td>
<td>12.9</td>
<td><sup>NS</sup> 8.6</td>
<td><sup>NS</sup> 11.1</td>
<td></td>
<td><sup>NS</sup> 24.7</td>
<td><sup>NS</sup> 21.0</td>
<td></td>
</tr>
<tr class="odd">
<td>Douglas County, NE</td>
<td>6.5</td>
<td>12.7</td>
<td>6.2</td>
<td>11.4</td>
<td>7.8</td>
<td>17.8</td>
<td></td>
<td><sup>NS</sup> 13.5</td>
<td><sup>NS</sup> 15.5</td>
<td></td>
</tr>
<tr class="even">
<td>Otero County, NM</td>
<td>7.5</td>
<td>14.0</td>
<td>7.3</td>
<td>12.3</td>
<td>8.3</td>
<td>18.8</td>
<td></td>
<td>14.7</td>
<td>21.8</td>
<td></td>
</tr>
<tr class="odd">
<td>Bronx Borough, NY</td>
<td>11.1</td>
<td>25.1</td>
<td>13.1</td>
<td>24.1</td>
<td>9.7</td>
<td>27.7</td>
<td></td>
<td><sup>NS</sup> 26.7</td>
<td><sup>NS</sup> 27.0</td>
<td></td>
</tr>
<tr class="even">
<td>Rockland County, NY</td>
<td>8.2</td>
<td>15.6</td>
<td>6.8</td>
<td>14.1</td>
<td>11.0</td>
<td>19.3</td>
<td></td>
<td>38.0</td>
<td>16.3</td>
<td></td>
</tr>
<tr class="odd">
<td>Franklin County, OH</td>
<td>6.5</td>
<td>12.7</td>
<td>6.1</td>
<td>11.2</td>
<td>7.7</td>
<td>17.9</td>
<td></td>
<td>16.7</td>
<td>10.6</td>
<td></td>
</tr>
<tr class="even">
<td>Multnomah County, OR</td>
<td>6.6</td>
<td>11.8</td>
<td>6.2</td>
<td>10.8</td>
<td>8.0</td>
<td>15.4</td>
<td></td>
<td>15.5</td>
<td>9.5</td>
<td></td>
</tr>
<tr class="odd">
<td>Fulton County, PA</td>
<td>7.7</td>
<td>15.8</td>
<td>7.0</td>
<td>15.5</td>
<td>8.8</td>
<td>17.1</td>
<td></td>
<td><sup>NS</sup> 25.4</td>
<td><sup>NS</sup> 19.1</td>
<td></td>
</tr>
<tr class="even">
<td>Schuylkill County, PA</td>
<td>7.0</td>
<td>15.9</td>
<td>7.1</td>
<td>15.1</td>
<td>7.6</td>
<td>19.8</td>
<td></td>
<td>31.2</td>
<td>20.9</td>
<td></td>
</tr>
<tr class="odd">
<td>Sevier County, TN</td>
<td>8.4</td>
<td>15.6</td>
<td>7.6</td>
<td>14.8</td>
<td>10.0</td>
<td>17.8</td>
<td></td>
<td><sup>NS</sup> 21.1</td>
<td><sup>NS</sup> 18.1</td>
<td></td>
</tr>
<tr class="even">
<td>Fort Bend County, TX</td>
<td>7.7</td>
<td>15.5</td>
<td>6.8</td>
<td>13.7</td>
<td>9.9</td>
<td>20.3</td>
<td></td>
<td><sup>NS</sup> 18.8</td>
<td><sup>NS</sup> 13.2</td>
<td></td>
</tr>
<tr class="odd">
<td>Harris County, TX</td>
<td>7.9</td>
<td>16.6</td>
<td>7.3</td>
<td>15.9</td>
<td>9.4</td>
<td>19.0</td>
<td></td>
<td>19.3</td>
<td>12.1</td>
<td></td>
</tr>
<tr class="even">
<td>Starr County, TX</td>
<td>6.3</td>
<td>17.8</td>
<td>9.6</td>
<td>23.6</td>
<td>5.6</td>
<td>14.2</td>
<td></td>
<td><sup>NS</sup> 22.9</td>
<td><sup>NS</sup> 22.9</td>
<td></td>
</tr>
<tr class="odd">
<td>Zapata County, TX</td>
<td>6.0</td>
<td>18.8</td>
<td><sup>NS</sup> 7.5</td>
<td><sup>NS</sup> 21.4</td>
<td>5.7</td>
<td>12.9</td>
<td></td>
<td><sup>NS</sup> 31.3</td>
<td><sup>NS</sup> 25.1</td>
<td></td>
</tr>
<tr class="even">
<td>Petersburg City, VA</td>
<td>9.0</td>
<td>17.7</td>
<td>9.0</td>
<td>16.6</td>
<td>10.5</td>
<td>21.4</td>
<td></td>
<td><sup>NS</sup> 20.0</td>
<td><sup>NS</sup> 23.0</td>
<td></td>
</tr>
<tr class="odd">
<td>Yakima County, WA</td>
<td>9.6</td>
<td>15.9</td>
<td>7.9</td>
<td>15.6</td>
<td>12.6</td>
<td>17.2</td>
<td></td>
<td><sup>NS</sup> 21.6</td>
<td><sup>NS</sup> 21.7</td>
<td></td>
</tr>
<tr class="even">
<td>Ohio County, WV</td>
<td>7.4</td>
<td>15.4</td>
<td>6.5</td>
<td>14.6</td>
<td>10.4</td>
<td>18.4</td>
<td></td>
<td>38.8</td>
<td>18.1</td>
<td></td>
</tr>
<tr class="odd">
<td>Oneida County, WI</td>
<td>7.1</td>
<td>11.4</td>
<td>7.2</td>
<td>13.1</td>
<td>7.0</td>
<td>10.9</td>
<td></td>
<td><sup>NS</sup> 26.8</td>
<td><sup>NS</sup> 34.5</td>
<td></td>
</tr>
<tr class="even">
<td>Vilas County, WI</td>
<td>7.1</td>
<td>13.3</td>
<td><sup>NS</sup> 7.4</td>
<td><sup>NS</sup> 7.3</td>
<td>7.2</td>
<td>13.2</td>
<td></td>
<td>31.5</td>
<td>43.2</td>
<td></td>
</tr>
<tr class="odd">
<td colspan="11">NS – The ACS three-year average and Census 2000 sample
quality measure are not statistically significantly different for this
county.</td>
</tr>
</tbody>
</table>

+---------------------+-----+------+-------+------+---------+---------+
| # Table A-4. C      |     |      |       |      |         |         |
| omparison of Summar |     |      |       |      |         |         |
| y Allocation Rates  |     |      |       |      |         |         |
| for Population and  |     |      |       |      |         |         |
| Occupied Housing Un |     |      |       |      |         |         |
| it Items: ACS Three |     |      |       |      |         |         |
| -year Average and C |     |      |       |      |         |         |
| ensus 2000 Sample E |     |      |       |      |         |         |
| stimates, by County |     |      |       |      |         |         |
+=====================+=====+======+=======+======+=========+=========+
| **County**          | *   | **Ce | **ACS | **Ce | **ACS   | *       |
|                     | *AC | nsus | Self- | nsus | I       | *Census |
|                     | S** | Tot  | respo | Sel  | ntervie | I       |
|                     |     | al** | nse** | f-re | wer-res | ntervie |
|                     | **T |      |       | spon | ponse** | wer-res |
|                     | ota |      |       | se** |         | ponse** |
|                     | l** |      |       |      |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Pima County, AZ     | 6.6 | 11.1 | 7.3   | 9.8  | 6.1     | 15.3    |
+---------------------+-----+------+-------+------+---------+---------+
| Jefferson County,   | 7.9 | 15.3 | 10.5  | 13.2 | 5.5     | 22.1    |
| AR                  |     |      |       |      |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| San Francisco       | 8.2 | 14.0 | 9.0   | 12.2 | 7.3     | 19.3    |
| County, CA          |     |      |       |      |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Tulare County, CA   | 7.9 | 14.7 | 9.2   | 13.3 | 7.3     | 17.9    |
+---------------------+-----+------+-------+------+---------+---------+
| Broward County, FL  | 7.2 | 12.4 | 8.3   | 11.6 | 6.1     | 14.1    |
+---------------------+-----+------+-------+------+---------+---------+
| Upson County, GA    | 7.8 | 13.4 | 9.8   | 13.9 | 5.5     | 12.4    |
+---------------------+-----+------+-------+------+---------+---------+
| Lake County, IL     | 6.3 | 11.5 | 6.9   | 9.7  | 5.7     | 16.4    |
+---------------------+-----+------+-------+------+---------+---------+
| Miami County, IN    | 6.5 | 14.3 | 7.8   | 12.3 | 4.9     | 24.8    |
+---------------------+-----+------+-------+------+---------+---------+
| Black Hawk County,  | 6.5 | 11.0 | 7.2   | 9.5  | 6.0     | 17.4    |
| IA                  |     |      |       |      |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| De Soto Parish, LA  | 8.4 | 15.2 | 11.3  | 15.5 | 5.7     | 14.8    |
+---------------------+-----+------+-------+------+---------+---------+
| Calvert County, MD  | 5.6 | 10.1 | 6.4   | 9.3  | 4.6     | 12.5    |
+---------------------+-----+------+-------+------+---------+---------+
| Hampden County, MA  | 7.1 | 13.3 | 8.0   | 12.3 | 6.1     | 16.3    |
+---------------------+-----+------+-------+------+---------+---------+
| Madison County, MS  | 6.5 | 14.4 | 7.7   | 11.4 | 5.6     | 27.8    |
+---------------------+-----+------+-------+------+---------+---------+
| Iron County, MO     | 7.1 | 13.3 | ^NS^  | ^NS^ | 5.4     | 14.8    |
|                     |     |      | 9.6   | 12.5 |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Reynolds County, MO | 7.2 | 15.5 | ^NS^  | ^NS^ | 5.9     | 18.4    |
|                     |     |      | 10.5  | 14.9 |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Washington County,  | 6.6 | 13.9 | 9.0   | 13.3 | 5.1     | 15.1    |
| MO                  |     |      |       |      |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Flathead County, MT | 6.9 | 12.8 | 8.4   | 10.8 | 4.9     | 18.8    |
+---------------------+-----+------+-------+------+---------+---------+
| Lake County, MT     | 6.6 | 8.9  | 7.2   | 9.8  | ^NS^    | ^NS^    |
|                     |     |      |       |      | 6.1     | 8.8     |
+---------------------+-----+------+-------+------+---------+---------+
| Douglas County, NE  | 6.0 | 10.5 | 6.9   | 8.9  | 4.8     | 15.8    |
+---------------------+-----+------+-------+------+---------+---------+
| Otero County, NM    | 6.5 | 11.1 | 8.0   | 9.4  | 4.9     | 14.9    |
+---------------------+-----+------+-------+------+---------+---------+
| Bronx Borough, NY   | 9.4 | 19.4 | 13.5  | 18.7 | 7.0     | 21.0    |
+---------------------+-----+------+-------+------+---------+---------+
| Rockland County, NY | 7.3 | 12.4 | 7.6   | 11.3 | 7.3     | 15.3    |
+---------------------+-----+------+-------+------+---------+---------+
| Franklin County, OH | 5.5 | 10.6 | 6.2   | 8.8  | 4.8     | 15.5    |
+---------------------+-----+------+-------+------+---------+---------+
| Multnomah County,   | 6.2 | 10.1 | 6.7   | 8.8  | 6.0     | 13.9    |
| OR                  |     |      |       |      |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Fulton County, PA   | 7.6 | 12.1 | ^NS^  | ^NS^ | 6.4     | 13.6    |
|                     |     |      | 8.7   | 11.8 |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Schuylkill County,  | 6.3 | 12.0 | 7.1   | 11.1 | 4.8     | 16.1    |
| PA                  |     |      |       |      |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Sevier County, TN   | 7.3 | 12.7 | 8.4   | 11.4 | 6.0     | 15.5    |
+---------------------+-----+------+-------+------+---------+---------+
| Fort Bend County,   | 6.4 | 12.5 | 7.0   | 10.7 | 6.1     | 16.6    |
| TX                  |     |      |       |      |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Harris County, TX   | 6.8 | 13.7 | 8.1   | 12.9 | 6.1     | 15.5    |
+---------------------+-----+------+-------+------+---------+---------+
| Starr County, TX    | 4.7 | 12.1 | 11.5  | 16.1 | 3.0     | 10.2    |
+---------------------+-----+------+-------+------+---------+---------+
| Zapata County, TX   | 4.9 | 15.6 | 8.4   | 18.8 | 3.8     | 9.4     |
+---------------------+-----+------+-------+------+---------+---------+
| Petersburg City, VA | 7.9 | 15.2 | 10.6  | 14.7 | 5.7     | 17.0    |
+---------------------+-----+------+-------+------+---------+---------+
| Yakima County, WA   | 8.3 | 12.5 | 8.6   | 12.3 | 8.7     | 13.2    |
+---------------------+-----+------+-------+------+---------+---------+
| Ohio County, WV     | 7.6 | 12.1 | 7.5   | 11.3 | 7.7     | 14.4    |
+---------------------+-----+------+-------+------+---------+---------+
| Oneida County, WI   | 6.8 | 9.5  | ^NS^  | ^NS^ | 4.6     | 9.2     |
|                     |     |      | 7.7   | 10.2 |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| Vilas County, WI    | 6.7 | 11.5 | ^NS^  | ^NS^ | 5.7     | 11.5    |
|                     |     |      | 7.6   | 5.9  |         |         |
+---------------------+-----+------+-------+------+---------+---------+
| NS -- The ACS       |     |      |       |      |         |         |
| three-year average  |     |      |       |      |         |         |
| and Census 2000     |     |      |       |      |         |         |
| sample quality      |     |      |       |      |         |         |
| measure are not     |     |      |       |      |         |         |
| statistically       |     |      |       |      |         |         |
| significantly       |     |      |       |      |         |         |
| different for this  |     |      |       |      |         |         |
| county.             |     |      |       |      |         |         |
+---------------------+-----+------+-------+------+---------+---------+

**Appendix B**

**Design Factors Used for Standard Errors of Census Quality Measures**

For the self-response rates, unit nonresponse rates, and housing unit
completeness rate, the largest design factor (see Summary File 3
Technical Documentation, released in 2003 at
<http://www.census.gov/prod/cen2000/doc/sf3.pdf>) from the following
housing unit characteristics was used to calculate the census standard
errors.

-   Race of householder

```{=html}
<!-- -->
```
-   Age of householder

-   Type of residence

    For the population completeness rate, the largest design factor from
    the following population characteristics were used to calculate the
    census standard errors.

```{=html}
<!-- -->
```
-   Race

```{=html}
<!-- -->
```
-   Age

-   Household type and relationship

-   Family type

For the item allocation rates, the following table lists the items for
which an allocation rate was calculated, and the population/housing
characteristic group which most relates to that item. The design factor
for the population/housing characteristic group listed was applied to
the item allocation rate standard errors. The bold housing unit
allocation rate items are vacant housing units items.

Table B-1. Design Factors used to Calculate Standard Errors of Census
2000 Sample Item Allocation Rates

+------+------------------------------------+--------------------------+
| **G  | **Design Factor** Number range     | **Allocation Rate Item** |
| roup | CHAPTER**Population/Housing        |                          |
| Numb | Characteristic Group**             |                          |
| er** |                                    |                          |
+======+====================================+==========================+
| **Po |                                    |                          |
| pula |                                    |                          |
| tion |                                    |                          |
| Cha  |                                    |                          |
| ract |                                    |                          |
| eris |                                    |                          |
| tics |                                    |                          |
| and  |                                    |                          |
| Grou |                                    |                          |
| ps** |                                    |                          |
+------+------------------------------------+--------------------------+
| P1   | Age                                | Age                      |
+------+------------------------------------+--------------------------+
| P6   | Household type and relationship    | Relationship             |
+------+------------------------------------+--------------------------+
| P2   | Sex                                | Sex                      |
+------+------------------------------------+--------------------------+
| P3   | Race                               | Race                     |
+------+------------------------------------+--------------------------+
| P4   | Hispanic or Latino                 | Hispanic                 |
+------+------------------------------------+--------------------------+
| P5   | Marital Status                     | Marital Status           |
+------+------------------------------------+--------------------------+
| P15  | School enrollment                  | School enrollment        |
+------+------------------------------------+--------------------------+
|      |                                    | Grade attending          |
+------+------------------------------------+--------------------------+
| P14  | Educational attainment             | Educational attainment   |
+------+------------------------------------+--------------------------+
| P13  | Language spoken at home and        | Non-English language     |
|      | ability to speak English           |                          |
+------+------------------------------------+--------------------------+
|      |                                    | Language spoken          |
+------+------------------------------------+--------------------------+
|      |                                    | English ability          |
+------+------------------------------------+--------------------------+
| P9   | Place of birth                     | Place of birth           |
+------+------------------------------------+--------------------------+
| P10  | Citizenship status                 | Citizenship              |
+------+------------------------------------+--------------------------+
| P12  | Year of entry                      | Year of entry            |
+------+------------------------------------+--------------------------+
| P11  | Residence in 1995                  | Mobility status          |
|      |                                    |                          |
|      | Residence in 1995 (cont'd)         |                          |
+------+------------------------------------+--------------------------+
|      |                                    | Migration -- state       |
+------+------------------------------------+--------------------------+
|      |                                    | Migration -- county      |
+------+------------------------------------+--------------------------+
|      |                                    | Migration -- place       |
+------+------------------------------------+--------------------------+
| P7   | Disabled and employment disability | Vision or hearing        |
|      |                                    | difficulty               |
+------+------------------------------------+--------------------------+
|      |                                    | Physical difficulty      |
+------+------------------------------------+--------------------------+
|      |                                    | Mental difficulty        |
+------+------------------------------------+--------------------------+
|      |                                    | Self-care difficulty     |
+------+------------------------------------+--------------------------+
|      |                                    | Difficulty going out     |
+------+------------------------------------+--------------------------+
|      |                                    | Difficulty working at a  |
|      |                                    | job                      |
+------+------------------------------------+--------------------------+
| P37  | Grandparent status and             | Grandparent living at    |
|      | responsibility for grandchild      | home                     |
+------+------------------------------------+--------------------------+
|      |                                    | Responsible for          |
|      |                                    | grandchildren            |
+------+------------------------------------+--------------------------+
|      |                                    | Months responsible for   |
|      |                                    | grandchildren            |
+------+------------------------------------+--------------------------+
| P36  | Military service and veteran       | Served in armed forces   |
|      | status                             |                          |
+------+------------------------------------+--------------------------+
|      |                                    | Periods of military      |
|      |                                    | service                  |
+------+------------------------------------+--------------------------+
|      |                                    | Years of active duty     |
+------+------------------------------------+--------------------------+
| P20  | Employment status                  | Employment status        |
+------+------------------------------------+--------------------------+
| P26  | Place of work                      | Place of work - state    |
+------+------------------------------------+--------------------------+
|      |                                    | Place of work - county   |
+------+------------------------------------+--------------------------+
|      |                                    | Place of work - place    |
+------+------------------------------------+--------------------------+
| P27  | Means of transportation to work    | Transportation to work   |
+------+------------------------------------+--------------------------+
| P29  | Time leaving home to go to work    | Time of departure        |
+------+------------------------------------+--------------------------+
| P30  | Private vehicle occupancy          | Carpool size             |
+------+------------------------------------+--------------------------+
| P28  | Travel time to work                | Commuting time           |
+------+------------------------------------+--------------------------+
| P24  | Usual hours worked per week and    | When last worked         |
|      | weeks worked in 1999               |                          |
+------+------------------------------------+--------------------------+
|      |                                    | Weeks worked last year   |
+------+------------------------------------+--------------------------+
|      |                                    | Hours worked each week   |
+------+------------------------------------+--------------------------+
| P21  | Industry                           | Industry                 |
+------+------------------------------------+--------------------------+
| P22  | Occupation                         | Occupation               |
+------+------------------------------------+--------------------------+
| P23  | Class of worker                    | Class of worker          |
+------+------------------------------------+--------------------------+
| P31  | Type of Income in 1999             | Wages & salary income    |
+------+------------------------------------+--------------------------+
|      |                                    | Self-employment income   |
+------+------------------------------------+--------------------------+
|      |                                    | Interest, dividend, etc. |
|      |                                    | income                   |
+------+------------------------------------+--------------------------+
|      |                                    | Social security/railroad |
|      |                                    | retirement               |
+------+------------------------------------+--------------------------+
|      |                                    | Supplemental security    |
|      |                                    | income                   |
+------+------------------------------------+--------------------------+
|      |                                    | Public assistance        |
+------+------------------------------------+--------------------------+
|      |                                    | Retirement income        |
+------+------------------------------------+--------------------------+
|      |                                    | Other income             |
+------+------------------------------------+--------------------------+
|      |                                    | All income allocated     |
+------+------------------------------------+--------------------------+
| *    |                                    |                          |
| *Hou |                                    |                          |
| sing |                                    |                          |
| Unit |                                    |                          |
| Cha  |                                    |                          |
| ract |                                    |                          |
| eris |                                    |                          |
| tics |                                    |                          |
| and  |                                    |                          |
| Grou |                                    |                          |
| ps** |                                    |                          |
+------+------------------------------------+--------------------------+
| H5   | Tenure                             | Tenure                   |
|      |                                    |                          |
|      |                                    | Year moved in            |
+------+------------------------------------+--------------------------+
| H4   | Units in structure                 | **Units in               |
|      |                                    | structure/building       |
|      |                                    | size**                   |
+------+------------------------------------+--------------------------+
| H10  | Year structure built               | **Year built**           |
+------+------------------------------------+--------------------------+
| H11  | Rooms, bedrooms                    | **Rooms**                |
+------+------------------------------------+--------------------------+
|      |                                    | **Bedrooms**             |
+------+------------------------------------+--------------------------+
| H13  | Plumbing facilities                | **Complete plumbing**    |
+------+------------------------------------+--------------------------+
| H12  | Kitchen facilities                 | **Complete kitchen**     |
+------+------------------------------------+--------------------------+
|      |                                    | Telephone                |
+------+------------------------------------+--------------------------+
| H14  | House heating fuel                 | Heating fuel             |
+------+------------------------------------+--------------------------+
|      |                                    | Electricity cost         |
+------+------------------------------------+--------------------------+
|      |                                    | Gas cost                 |
+------+------------------------------------+--------------------------+
|      |                                    | Water and sewer cost     |
+------+------------------------------------+--------------------------+
|      |                                    | Other fuel cost          |
+------+------------------------------------+--------------------------+
| H16  | Vehicles available                 | Number of vehicles       |
+------+------------------------------------+--------------------------+
| H22  | Type of residence                  | **Business on property** |
+------+------------------------------------+--------------------------+
|      |                                    | **Lot size**             |
+------+------------------------------------+--------------------------+
|      |                                    | Agricultural sales       |
+------+------------------------------------+--------------------------+
| H8   | Gross rent                         | **Monthly rent**         |
+------+------------------------------------+--------------------------+
|      |                                    | **Meals in rent**        |
+------+------------------------------------+--------------------------+
| H19  | Mortgage status and selected       | Mortgage                 |
|      | monthly owner costs                |                          |
+------+------------------------------------+--------------------------+
|      |                                    | Mortgage payments        |
+------+------------------------------------+--------------------------+
|      |                                    | Payment includes         |
|      |                                    | property taxes           |
+------+------------------------------------+--------------------------+
|      |                                    | Payment includes         |
|      |                                    | insurance                |
+------+------------------------------------+--------------------------+
|      |                                    | Second mortgage payment  |
+------+------------------------------------+--------------------------+
|      |                                    | Yearly real estate taxes |
+------+------------------------------------+--------------------------+
|      |                                    | Yearly property          |
|      |                                    | insurance                |
+------+------------------------------------+--------------------------+
|      |                                    | Total cost on mobile     |
|      |                                    | home                     |
+------+------------------------------------+--------------------------+
| H7   | Value                              | **Value**                |
+------+------------------------------------+--------------------------+
| H6   | Occupancy status                   | **Vacancy status**       |
+------+------------------------------------+--------------------------+

######### Appendix C

######## **Quality Measures Scatter Plots for Counties**

This Appendix contains one dimensional scatter plots of the county-level
differences between the quality measures for the ACS three-year averages
and Census 2000 sample estimates.

Differences between the ACS three-year averages and the Census 2000
sample quality measures are located on the vertical axis; counties and,
in Figures C-4, C-5, and C-6, quality measures, are on the horizontal
axis. We sorted counties by their 100 percent count of census housing
units (for Figures C-4, C-5, and C-6, we sorted counties within each
quality measure). The sorts were in ascending order, from left to right.
For example, the difference for the county with the smallest count is
the left-most point in each graph (or quality measure), while the
difference for the county with the largest count is the right-most point
in each graph (or quality measure). We used a "jittering" process so
that we could plot the differences in this way. The "jittering" process
assigned a unique integer to each county so as to achieve this sort,
where the county with the smallest count received the smallest integer,
etc.

Counties with statistically significant differences are indicated by an
"X" on the scatter plots; counties whose differences are not
statistically significantly different are indicated by a circle. A
difference is defined to be the ACS three-year average quality measure
minus the Census 2000 sample quality measure. These graphs were produced
in SAS using data from the Quality Measures Comparison Files.

![](media/image23.wmf)

![](media/image24.wmf)

![](media/image25.wmf)

![](media/image26.wmf)

![](media/image27.wmf)

![](media/image28.wmf)

![](media/image29.wmf)

> ![](media/image30.wmf)

######### Appendix D

**Quality Measures Scatter Plots for Tracts**

This Appendix contains one dimensional scatter plots of the tract-level
differences between the quality measures for the ACS three-year averages
and Census 2000 sample estimates. We grouped all of the tract-level
differences in each graph by tract group. So, there are five sets of
one-dimensional scatter plots in each graph, one set of plots for each
tract group. Each graph represents one quality measure.

Differences between the ACS three-year averages and the Census 2000
sample quality measures are located on the vertical axis; tracts and
tract groups are on the horizontal axis. We sorted tracts within each
tract group by their 100 percent count of census housing units. The
sorts were in ascending order, from left to right, within each tract
group. For example, the difference for the tract with the smallest count
is the left-most point within each tract group, while the difference for
the tract with the largest count is the right-most point within each
tract group. We used a "jittering" process so that we could plot the
differences in this way. Within each tract group, the "jittering"
process assigned a unique integer to each tract so as to achieve this
sort, where the tract with the smallest count received the smallest
integer, etc.

The tract groups are:

-   Group 1 - tracts in small counties (under 100,000 persons) and tract
    population greater than 500 (207 tracts)

-   Group 2 - tracts in medium counties (100,000 - 1,000,000 persons)
    and tract population between 500 and 4000 (592 tracts)

-   Group 3 - tracts in medium counties (100,000 - 1,000,000 persons)
    and tract population greater than 4000 (580 tracts)

-   Group 4 - tracts in large counties (1,000,000+ persons) and tract
    population between 500 and 4000 (401 tracts)

-   Group 5 - tracts in large counties (1,000,000+ persons) and tract
    population greater than 4000 (470 tracts)

Tracts with statistically significant differences are indicated by an
"X" on the scatter plots; tracts whose differences are not statistically
significantly different are indicated by a circle. The difference is
defined to be the ACS three-year average quality measure minus the
Census 2000 sample quality measure. These graphs were produced in SAS
using data from the Quality Measures Comparison Files.

![](media/image31.wmf)

![](media/image32.wmf)

![](media/image33.wmf)

![](media/image34.wmf)

![](media/image35.wmf)

![](media/image36.wmf)

![](media/image37.wmf)

[^1]: Tracts in Fort Bend County and Harris County were excluded because
    of their low sampling rate compared to the ACS five-year design
    level.

[^2]: In mailback TEAs, respondents were asked to return their completed
    census form by mail. This could have been a mailout/mailback TEA
    where the census form was delivered to the housing units by the
    United States Postal Service (USPS), or an update/leave TEA where
    the form was delivered in person by a census enumerator. In
    list/enumerate TEAs a form was delivered in person by a census
    enumerator, and then completed at the time of delivery with the help
    of the census enumerator.