38374 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

DEPARTMENT OF COMMERCE

Bureau of the Census

Accuracy and Coverage Evaluation;

Statement on the Feasibility of Using

Statistical Methods To Improve the

Accuracy of Census 2000

AGENCY: Bureau of the Census,

Department of Commerce.

ACTION: Notice.

SUMMARY: The Director of the Census

has issued Accuracy and Coverage

Evaluation; Statement on the Feasibility

of Using Statistical Methods to Improve

the Accuracy of Census 2000, his

statement on the feasibility of using

modern statistical methods to correct

Census 2000 counts. The document sets

forth the rationale for the Census

Bureau’s preliminary determination that

(1) statistically corrected census data

can be produced within the time frame

required by law and (2) that statistically

corrected data will be more accurate.

The Secretary has adopted the Director’s

analysis and conclusions in a written

decision forwarded to the Director. For

public information, set forth below is

Accuracy and Coverage Evaluation;

Statement on the Feasibility of Using

Statistical Methods to Improve the

Accuracy of Census 2000, as well as

three related memoranda (the Director’s

memorandum transmitting the

document to the Secretary, the

Secretary’s memorandum to the

Director, and a supporting legal opinion

of the Commerce Department’s General

Counsel).

Authority: 13 U.S.C. 141, 13 U.S.C. 195.

William G. Barron,

Deputy Director.

June 12, 2000.

MEMORANDUM FOR The Honorable

William Daley, Secretary of

Commerce

Through: Robert Shapiro, Under

Secretary for Economic Affairs

From: Kenneth Prewitt, Director

Subject: Accuracy and Coverage

Evaluation: Statement on the

Feasibility of Using Statistical

Methods to Improve the Accuracy of

Census 2000

Attached is my statement on the

feasibility of using modern statistical

methods to correct Census 2000 counts

as stipulated by the U.S. Supreme

Court’s decision in Department of

Commerce v. United States House of

Representatives (January 1999). This

statement was prepared after extensive

discussions with the U.S. Census

Bureau’s senior staff and review of all

relevant documents.

The Census Bureau is committed to

making its data as accurate as possible

for all uses. This document sets forth

the rationale for the Census Bureau’s

preliminary determination that (1)

statistically corrected census data can be

produced within the time frame

required by law and (2) that statistically

corrected data will be more accurate.

ACCURACY AND COVERAGE

EVALUATION

STATEMENT ON THE FEASIBILITY OF

USING STATISTICAL METHODS TO

IMPROVE THE ACCURACY OF

CENSUS 2000

Table of Contents

Executive Summary

Background and Overview

Uses of Decennial Census Data

The Differential Undercount

Summary of Census 2000 Operations

The Accuracy and Coverage Evaluation

Methodology

The A.C.E. in Brief

The Sample Design

Conducting the Survey

Dual System Estimation

Assessment of Feasibility

The Definition of Feasibility

Operational Feasibility

Release of Data Products for Use in

Redistricting

Operational Considerations

Resource Considerations

The Census 2000 Dress Rehearsal

Technical Feasibility

Defining Numeric and Distributive

Accuracy

Importance of and Relationship Between

the Two Types of Accuracy

Impact of the A.C.E. on Accuracy

Historical Experience with Coverage

Measurement Surveys

Demonstrates Feasibility

The 1980 Census Experience

Early Research and Development for the

1990 Census

Litigation Challenging Decision to Halt

1990 Adjustment-Related Planning

Activities

Conducting the 1990 Census and Deciding

Against Adjustment

Postcensal Estimates and Survey Controls

Decision

Early Census 2000 Planning

The Census 2000 Dress Rehearsal

External Review

A.C.E. Implementation Issues

Measuring Accuracy

Assessment of Issues Emerging from 1990

The Proper Standard to Use in Deciding

Whether to Statistically Correct the

Counts for Non-Apportionment Purposes

Numeric v. Distributive Accuracy

Correlation Bias

Accuracy at Different Geographic Levels

Consistency with Demographic Analysis

Timing

Level of Sampling Variance/Smoothing

Level of Nonsampling Error/Bias

Enhancements to the Matching Process

Enhancements to Computer Processing

Enhancements to Minimize Missing Data

Homogeneity and the Synthetic

Assumption

Additional Design Changes from 1990

Use of the Telephone in A.C.E.

Interviewing

New Treatment to Account for Movers

Search Area for Matching

Reporting More Than One Race

Making the Final Decision

Conclusions

Bibliography

Executive Summary

This document sets forth the rationale

for the Census Bureau’s preliminary

determination that (1) it is feasible to

produce statistically corrected census

data within the time frame required by

law and (2) the statistically corrected

data will be more accurate.

Data from the decennial census are

used to produce the state population

totals for congressional apportionment.

Additionally, detailed state data are

used for redistricting, federal funds

distribution, and other public and

private sector purposes. Section 141(b)

of Title 13 requires the Secretary of

Commerce to report state population

totals from Census 2000 to the President

by January 1, 2001. Section 141(c)

requires the Census Bureau to report

redistricting data directly to the states

by April 1, 2001.

The Census Bureau is committed to

making its data as accurate as possible

for all uses. In accordance with a 1999

Supreme Court ruling, the Census

Bureau will not use statistical sampling

to produce the state population totals

used for congressional apportionment.

Because the Census Bureau expects it

can produce more accurate data by

supplementing traditional enumeration

procedures with statistical sampling, it

plans to use these statistical methods to

produce the more detailed data required

for redistricting and federal program

purposes.

Prior to April 1, 2001, the Census

Bureau will have completed an

enumeration of the American

population, including a coverage

measurement survey, that is designed to

improve the accuracy of the initial

counts. The coverage measurement

survey, called the Accuracy and

Coverage Evaluation (A.C.E.), is based

on the established statistical method

known as Dual System Estimation (DSE)

and is designed to correct for missed

individuals or erroneous enumerations

in the traditional enumeration. The

method of Demographic Analysis will

also be used to evaluate the

completeness of population coverage in

Census 2000 at the national level, and

to assess changes from previous

censuses.

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38375

1Constitution, Art. I, Sec. 2, cl. 3.

The operations used to produce the

apportionment counts are designed with

the goal of counting and correctly

locating every individual residing in the

United States on April 1, 2000, and also

to count federal employees and their

dependents living overseas as of that

date. This goal cannot be completely

and accurately realized. Every decennial

census, from 1790 to 1990, has included

in the census counts some who should

have been excluded, and has missed

some who should have been included.

The first source of error leads to an

overcount; the second source to an

undercount. Every census for which the

effect of these errors has been

systematically measured has shown a

net undercount—that is, the number of

residents who were missed was greater

than the number of erroneous

enumerations.

Furthermore, in studies going back to

1940, the Census Bureau has

documented and measured not only an

overall net undercount, but also a higher

net differential undercount for the Black

population than for the non-Black

population. Studies from the 1990

census also indicate differentially

higher net undercounts for the Hispanic

population and American Indians on

reservations, compared to the White

population. This persistent problem of

differential undercounts is the most

significant error for the population

totals obtained through the traditional

enumeration. As part of the operations

for Census 2000, the Census Bureau will

conduct the A.C.E., which is designed to

improve census accuracy by increasing

overall coverage and reducing the

differential undercount. The A.C.E. also

corrects for the smaller, though not

insignificant, overcount that occurs

when erroneous enumerations are

included in the census.

The Census Bureau has determined

that the A.C.E. is operationally and

technically feasible and expects, barring

unforeseen operational difficulties that

would have a significant effect on the

quality of the data, that these corrected

data will be more accurate than the

uncorrected data for their intended

purposes. This determination is based

on more than 20 years of Census Bureau

research and experience with coverage

measurement surveys using DSE and is

supported by external experts in

statistical methodology. From these

years of experience, Census Bureau

statisticians have a comprehensive

understanding of the technical

underpinnings of DSE. This

understanding has guided the design of

the A.C.E., allowing the Census Bureau

to focus on the completeness and

quality of the estimates of the

population corrected for estimated net

census error.

It is possible, though very unlikely,

that problems with census operations

could lead the Census Bureau to

conclude that the data are not of

sufficient quality for their intended

purposes. These problems could occur

in the operations leading to production

of the apportionment counts and/or in

the operations leading to the production

of the corrected counts. This document

does not address factors that the Census

Bureau will consider in its

determination that the apportionment

counts are of sufficient quality to be

used for their intended purposes.

Because this document does focus on

the feasibility of using statistical

methods to improve the accuracy of

Census 2000 for purposes subsequent to

the production of apportionment

counts, it discusses the review process

for the final decision on whether to

release statistically corrected data. This

review process will be based on a

determination of whether the A.C.E.

operations were conducted in a way that

met expectations. In the fall of 2000, the

Census Bureau will present this review

process to the statistical community and

other interested parties.

Background and Overview

Census data are critically important in

achieving equitable political

representation and fair allocation of

resources. Finding and enumerating

approximately 275 million individuals

in the correct location is, of course, an

extremely challenging task. The

traditional decennial census misses

certain identifiable population groups at

greater rates than others and therefore

contains inherent inaccuracies. The

Census Bureau designed the Accuracy

and Coverage Evaluation (A.C.E.) using

proven statistical methodologies to

correct for this differential undercount

and thereby make the census more

accurate.

Uses of Decennial Census Data

The Constitution requires that a

census of the nation’s population be

taken every 10 years to reapportion seats

in the House of Representatives,1 but

the information provides more than just

state-by-state population totals. State

and local governments use census data

to draw legislative districts of equal

population to comply with the

constitutional ‘‘one-person-one-vote’’

mandate and the statutory requirements

of the Voting Rights Act. The federal

government distributes billions of

dollars in grants according to

population-based formulae that rely on

census data. Federal, state, local and

tribal officials study the patterns of

detailed census data before constructing

hospitals, highways, bridges, and

schools. Businesses, large and small,

have come to depend on the Census

Bureau’s population, income, education,

and housing data to make informed

decisions about locating new offices,

shops, and factories, and finding

markets for new products and services.

Census data also serve as definitive

benchmarks for many of the household

surveys conducted by federal agencies.

As will be explained in more detail

below, the Census Bureau has designed

the A.C.E. so that it will produce

statistically corrected census data down

to the block level. Census blocks are the

‘‘building blocks’’ employed by users of

census data. The Census Bureau does

not define the aggregations employed by

data users; it provides the data that

users can tabulate as needed for their

programmatic purposes. For example,

an administrator distributing funds

under the Elementary and Secondary

Education Act might need to distribute

funds tabulated to school districts,

which can range in size from large

counties and cities to small towns and

districts, while a state official

responsible for redistricting might need

to aggregate and re-aggregate census

blocks into many different

configurations to satisfy the

requirements of the Voting Rights Act,

42 U.S.C. § 1971 et seq.

38376 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

2The National Academy of Sciences agrees that

accuracy at the block level is not an appropriate

criterion of accuracy, that accuracy should be

evaluated at aggregated levels. See Andrew A.

White and Keith F. Rust, eds., Preparing for the

2000 Census: Interim Report II (Washington, D.C.:

National Academy Press, 1997), 11–12.

3Bureau of the Census, ‘‘Report to Congress—The

Plan for Census 2000,’’ originally issued July 1997,

revised and reissued August 1997, 2–6.

4 Ibid., 3.

5Howard Hogan, ‘‘The 1990 Post-Enumeration

Survey: Operations and Results,’’ Journal of the

American Statistical Association 88 (September

1993): 1054, Table 3.

The A.C.E. was designed to

accommodate the needs of data users by

allowing them to aggregate census

blocks as appropriate for their particular

program purposes. The accuracy of

aggregated census data is more

important than the accuracy of any

particular block because data users rely

on aggregated data, not block-level

data.2 Different types of accuracy and

how they can be assessed at various

levels of aggregation are reviewed

below.

This recitation of the uses of census

data illustrates the importance of taking

as accurate a census as possible by

reducing the differential undercounts of

geographic areas and demographic

groups. The belief that the census

should be as accurate as possible has

motivated the Census Bureau for more

than 20 years to develop techniques to

reduce the differential undercount.

The Differential Undercount

The Census Bureau has documented

and measured a substantial differential

undercount since the 1940 census.3

After the 1940 census, Census Bureau

statisticians and academic researchers

refined a statistical technique known as

Demographic Analysis, a technique that

measures coverage trends as well as

differences in coverage by age, sex, and

race. Demographic Analysis uses

records and estimates of births, deaths,

immigration, emigration, and Medicare

enrollments to develop estimates of the

population at the national level,

independently from the census.

Demographic Analysis, though not

without its errors, reveals the

persistence of the differential

undercount that exists between the

Black and the non-Black populations.

The following table illustrates this

differential:

DEMOGRAPHIC ANALYSIS ESTIMATES OF PERCENTAGE NET UNDERCOUNT, BY RACE: 1940–1990

1940 1950 1960 1970 1980 1990

Percent:

Total .................................................................................................. 5.4 4.1 3.1 2.7 1.2 1.8

Black ................................................................................................. 8.4 7.5 6.6 6.5 4.5 5.7

Non-Black ......................................................................................... 5 3.8 2.7 2.2 0.8 1.3

Percentage Point Difference:

Black/Non-Black ................................................................................ 3.4 3.6 3.9 4.3 3.7 4.4

Source: J.G. Robinson and others,

‘‘Estimates of Population Coverage in

the 1990 United States Census Based on

Demographic Analysis,’’ Journal of the

American Statistical Association 88,

(September 1993): 1065.

The 1990 census revealed that the

Black population was not the only

group undercounted differentially.

Children were much more likely than

adults to have been undercounted in the

1990 census. While children under the

age of 18 represented 26 percent of the

total national population that year, they

accounted for 52 percent of the net

estimated undercount as estimated by

the 1990 Post-Enumeration Survey

(PES).4 Another characteristic that

affected the likelihood of being missed

in the census was tenure, whether one

rents or owns. Renters were more likely

to have been left out of the 1990 count.

The 1990 PES found higher undercounts

among renters than for owners.5 As the

chart below demonstrates, a substantial

differential undercount also was

estimated in 1990 for Hispanics and

American Indians on reservations:

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38377

6Bureau of the Census, ‘‘Assessment of Accuracy

of Adjusted Versus Unadjusted 1990 Census Base

for Use in Intercensal Estimates,’’ Report of the

Committee on Adjustment of Postcensal Estimates,’’

7 August 1992, Attachment 3A, Table 2, later

referred to as CAPE; and Bureau of the Census,

‘‘Report to Congress—the Plan for Census 2000,’’ 4.

7Hogan, ‘‘The 1990 Post-Enumeration Survey:

Operations and Results,’’ 1054, Table 3.

8Barry Edmonston and Charles Schultze, eds.,

Modernizing the U.S. Census (Washington, D.C.:

National Academy Press, 1995), 44. The cost for

Census 2000 is currently estimated to be over $50

per housing unit in current dollars, indicating the

increasingly greater cost of taking a census using

traditional methods.

9 Department of Commerce v. House of

Representatives, 119 S.Ct. 765 (1999).

10The Census Bureau’s original plan to use

sampling was to conduct an Integrated Coverage

Measurement (ICM) survey to produce a onenumber census through the use of statistical

sampling (‘‘Report to Congress—The Plan for

Census 2000,’’ 29–32). The Census Bureau dropped

its plans to conduct an ICM after the Supreme Court

ruled that sampling could not be used to produce

the apportionment counts.

Within each demographic group, the

undercount for renters was considerably

higher than for owners. For example,

the estimated undercount was 6.5

percent for Black renters versus only 2.3

percent for Black owners.7

The differential undercount is a

longstanding problem and one that the

Census Bureau has not been able to

solve despite increased efforts and

resources. The National Academy of

Sciences has calculated that the per

housing unit cost of the census, in 1990

constant dollars, increased from less

than $10 per housing unit in 1960, to

$11 per housing unit in 1970, to $20 per

housing unit in 1980, and to $25 per

housing unit in 1990.8 This steady

increase in unit cost from 1960 to 1990,

in large part due to increased efforts to

reduce coverage errors, did not result in

any appreciable reduction in the

differential undercount.

The differential undercount clearly

affects census accuracy. When

identified areas and demographic

groups are differentially undercounted,

the relative population shares across

states and sub-state areas are incorrect.

Census data also provide the foundation

for a large number of federal

demographic statistics and household

statistical surveys. These data are also

extensively used by the private sector.

Inaccuracies in the decennial census are

carried over into these many other

statistical series, and therefore, the

persistent differential undercount has

far-reaching consequences across public

and private sector programs based on

census data.

Summary of Census 2000 Operations

The Supreme Court determined in

1999 that Title 13 statutorily precludes

the use of sampling to produce

congressional apportionment counts.9

Accordingly, the plan for Census 2000,

as outlined in the Updated Summary:

Census 2000 Operational Plan (February

1999), is to produce apportionment

numbers without the use of statistical

sampling by January 1, 2001. Rather

than conducting the Integrated Coverage

Measurement (ICM) survey 10 to

produce statistically corrected numbers

as part of the original Census 2000 plan,

the plan now includes the A.C.E., which

will produce statistically corrected

numbers for non-apportionment uses of

the data.

Within the constraint of the 1999

Supreme Court decision, the Census

Bureau is committed to producing the

most accurate data possible without the

use of sampling for purposes of

apportionment. The constraint does not

apply to non-apportionment uses, and

the Census Bureau also remains

committed to producing the most

accurate data possible for these other

uses by implementing the A.C.E. As a

prelude to the discussion of the A.C.E.,

this paper will briefly review basic

census operations to be conducted prior

to the A.C.E. A more extensive

explanation of the operations for Census

2000 can be found in the Census 2000

Operational Plan.

The Census Bureau uses three basic

data collection methods: mailout/

mailback (where the Census Bureau

mails questionnaires to housing units on

the address list and the residents mail

them back), update/leave (where Census

Bureau workers deliver questionnaires

at the same time they update the

address list, and the residents mail them

38378 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

11A more extensive description of the A.C.E. can

be found in Howard Hogan’s paper, ‘‘Accuracy and

Coverage Evaluation: Theory and Application’’,

prepared for the February 2–3, 2000, DSE Workshop

of the National Academy of Sciences Panel to

Review the 2000 Census; and Bureau of the Census,

‘‘Accuracy and Coverage Evaluation: Overview of

Design’’, by Danny R. Childers and Deborah A.

Fenstermaker, DSSD Census Procedures and

Operations Memorandum Series S–DT–02, 11

January 2000.

back), and list/enumerate (where Census

Bureau enumerators create the address

list while canvassing their assignment

areas and conducting interviews with

respondents). Individuals can also

respond to the census through the

Internet or by telephone. The Be

Counted program provides an additional

means for people to be included in the

census by allowing them to fill out a

blank form made available in various

public locations. Special enumeration

procedures are followed for remote parts

of Alaska, for locations containing a

concentration of persons with a

transient lifestyle (e.g., trailer parks,

marinas, and campgrounds), for group

quarters (e.g., prisons and long-term

care facilities), and for people with no

usual residence.

After allowing a reasonable amount of

time for respondents to mail back their

questionnaires, the Census Bureau

conducts an operation called

nonresponse followup (NRFU), which

involves conducting a field followup of

housing units that do not return their

questionnaires by mail. A census

enumerator will make up to six attempts

to contact housing units that appear

occupied to secure an interview. If an

interview cannot be obtained, the

enumerator attempts to interview a

proxy respondent, that is, a neighbor,

rental agent, building manager, or other

knowledgeable individual.

A number of other operations are

being implemented to ensure as

complete coverage as possible in the

initial enumeration. Computer edits are

performed on mail-return

questionnaires to identify those that

may contain missing persons and those

that contain large households (more

than six persons). Interviewers conduct

telephone interviews with these

households during the coverage edit

followup operation in order to obtain

accurate data about the persons residing

there. Another operation, coverage

improvement followup, is conducted

after NRFU. This operation includes an

interviewer recheck of housing units

classified as vacant or nonexistent

during NRFU to ensure that no units

have been misclassified. Finally, all

major operations of the Census 2000

plan are subjected to enhanced quality

assurance (QA) activities designed to

detect and correct errors before they

affect accuracy or data quality.

The Census Bureau also designed and

implemented an enhanced marketing

and partnership program that provides

an integrated communications effort to

increase both awareness of the

decennial census and public

cooperation. The marketing program is

designed around the first-ever paid

advertising campaign, including a

national media campaign aimed at

increasing mail response, targeted

advertising directed at raising mail

response among historically

undercounted populations, and special

advertising messages and campaigns

targeted to hard-to-enumerate

populations. In the partnership

program, the Census Bureau is working

nationwide with state and local partners

to encourage all individuals to respond

to the census.

After the data collection efforts have

been completed, the data are processed

through a number of computer

operations for unduplication of multiple

responses for the same housing unit and

for editing of inconsistent or missing

responses. For items that are not

reported by respondents, the Census

Bureau uses the statistical process of

imputation to determine a response. The

data are then tabulated, and the

tabulations and other statistical

aggregations are released.

The Accuracy and Coverage Evaluation

Methodology

Following the initial census, the

Census Bureau will conduct the A.C.E.

Key components of the A.C.E. include

the sample design, the survey itself, and

the Dual System Estimation (DSE) used

to compute the estimates of the true

population.11

The A.C.E. in Brief

The A.C.E. methodology planned for

Census 2000 involves comparing

(matching) the information from an

independent sample survey to initial

census records. In this process, the

Census Bureau conducts field

interviewing and computerized and

clerical matching of the records. Using

the results of this matching, the Census

Bureau will apply the statistical

methodology of DSE (described below)

to develop coverage correction factors

for various population groups. The

results will then be applied to the

census files to produce all required

Census 2000 tabulations, other than

apportionment. The A.C.E. can be

summarized as follows:

• Select a stratified random sample of

blocks for the A.C.E.

• Create an independent list of

housing units in the sample of A.C.E.

blocks.

• Begin conducting telephone

interviews of mail return housing units

on a subset of the independent list.

• After the initial census nonresponse

followup, conduct a personal visit

interview at every housing unit on the

independent list not already

interviewed by telephone.

• Match the results of the A.C.E.

interview to the initial census.

• Resolve cases that may not match

but that require additional information

by conducting a personal visit followup

interview.

• Use information from other similar

people to impute missing information.

• Categorize the A.C.E. data by age,

sex, tenure, and other appropriate

predefined variables into groupings

called post-strata.

• Calculate the coverage correction

factors using DSE, that is, determine the

extent to which people in each poststratum have been over- or

undercounted by the initial census.

• Apply the coverage correction

factors to correct the initial census data.

• Tabulate the statistically corrected

census results.

The Sample Design

For the 2000 A.C.E., the Census

Bureau selected a stratified random

sample of blocks designed to be

representative of racial and ethnic

composition; tenure (owner or renter);

and other variables. The sample consists

of approximately 11,800 block clusters

with approximately 314,000 housing

units. The sample is designed to provide

sufficient precision to estimate the true

population for groupings of the

population known as post-strata. Each

person belongs to one and only one

post-stratum. Post-strata are constructed

with the goal of grouping individuals

who have a similar probability of having

been included in the initial census.

Census 2000 post-stratification variables

include race, ethnicity, age, sex, tenure,

mail return rate, and metropolitan

status/census enumeration method. For

example, one post-stratum would

include non-Hispanic Black males, aged

18–29, in non-owner units, in mailout/

mailback areas of metropolitan

statistical areas with 500,000 or more

population, in tracts with a low mail

return rate in the census. By comparing

the estimated true population based on

the dual system estimate for each poststratum to the number of individuals

counted in the initial census

enumeration for each post-stratum, the

Census Bureau estimates over- and

undercounts for each post-stratum.

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38379

12Michael L. Cohen, Andrew A. White, and Keith

F. Rust, Measuring a Changing Nation—Modern

Methods for the 2000 Census (Washington, D.C.:

National Academy Press, 1999), 31; and Kirk M.

Wolter, ‘‘Some Coverage Error Models for Census

Data,’’ Journal of the American Statistical

Association 81 (June 1986): 338.

13Production of these estimates is discussed in

more detail in Bureau of the Census, ‘‘Accuracy and

Coverage Evaluation Survey: Dual System

Estimation,’’ by Donna Kostanich and Richard

Griffin, DSSD Census 2000 Procedures and

Operations Memorandum Series #Q–20, 12 January

2000.

Conducting the Survey

Essential to the proper conduct of the

A.C.E. is the need to ensure that the

A.C.E. and the initial census are

operationally independent.

Independence requires that the

probability of a particular household or

person being included in the A.C.E. is

not affected by the initial census

operations and that the probability of

people being included in the initial

census is not affected by A.C.E.

operations. Such independence is a

critical criterion for DSE.

The A.C.E. independent interview is

conducted by separately hired and

trained staff through the use of

Computer Assisted Personal

Interviewing (CAPI) either by telephone

or in person. CAPI is a method of data

collection using a laptop computer in

which the questions to be asked are

displayed on the screen and responses

are entered directly into the computer.

The Census Bureau expects that the use

of CAPI will improve the accuracy of

the A.C.E. interview. To get an early

start for the A.C.E. interviewing, where

possible, a telephone interview using

CAPI may be conducted for households

where the census questionnaire has

been completed and for which a

telephone number was obtained. This

activity is carried out concurrently with

the initial census followup of

nonresponse households. The door-todoor interviewing with CAPI does not

begin until the initial census

nonresponse followup is nearly

completed in a given block cluster. The

A.C.E. enumerators will attempt to

secure an in-person interview with a

household member. If the interview

cannot be obtained, the enumerator will

interview a proxy respondent.

After the A.C.E. independent

interviews have been completed,

computer matching between the initial

census and the A.C.E. person records is

carried out, followed by a clerical

matching operation using an automated

review system. The matching process

allows the Census Bureau to determine

who may have been missed by the

initial census or to determine erroneous

enumerations. It should be noted that

the census can miss either entire

households or individuals within

households. This is also the case for

erroneous enumerations.

The Census Bureau has carefully

designed the A.C.E. to minimize

matching errors. Incorrect matching

generally results either from errors

caused by incomplete, inaccurate, or

conflicting data, or from errors where a

poor match decision was made even

though the data were sufficient. It is

critical that the matching be as accurate

as possible. Accordingly, as necessary,

the Census Bureau conducts a personal

visit follow-up operation to obtain the

additional information needed to

accurately code A.C.E. and census

nonmatches. After this followup, the

Census Bureau conducts a final clerical

matching operation.

Even after this intense effort,

occasionally some information will still

be missing, either person characteristics,

status of enumeration in the initial

census, or match status for A.C.E. cases

that could not be resolved. Before any

calculations can be made to determine

the estimated true population, missing

person characteristics, initial census

enumeration status, and A.C.E. match

status must be resolved. Missing person

characteristics such as age, race, sex,

and tenure are statistically imputed

from data reported for other household

members or from similar households in

the geographic area. For unresolved

cases, the Census Bureau uses statistical

imputation methodology to impute

probabilities of being correctly

enumerated or matched. The Census

Bureau then estimates the true

population by using these results in

Dual System Estimation.

Dual System Estimation

DSE is an established and accepted

statistical technique that is also referred

to as ‘‘capture/recapture.’’ 12 Because

the Census Bureau has conducted years

of research into the likelihood that

people of varying characteristics will be

included in the census enumeration

(this likelihood is known as inclusion

probability), it is able to divide the

nation’s population into post-strata.

Each post-stratum is defined so as to

contain people with a similar

probability of being included in the

initial census. At the conclusion of the

A.C.E. processes described previously,

data are available for each post-stratum

to calculate a dual system estimate.13

The dual system estimate is an

estimate of the true population total for

each post-stratum. The dual system

estimates are then used to calculate a

coverage correction factor for each poststratum. The coverage correction factor

is a ratio of the dual system estimate

(the estimate of the true population) to

the initial census count. These factors

are then applied to correct the initial

census data files. For example, if the

coverage correction factor for nonHispanic Black males, aged 18–29, in

non-owner units, in mailout/mailback

areas of metropolitan statistical areas

with 500,000 or more population, in a

tract with a low mail return rate in the

census, is 1.02, then for every 100 such

person records counted in the census in

those areas, two numerical records will

be added. Once these factors are

applied, the corrected population

estimates are created and tabulated.

Assessment of Feasibility

Section 195 of the Census Act states

that ‘‘the Secretary shall, if he considers

it feasible, authorize the use of

sampling,’’ but the term ‘‘feasible’’ is not

defined. As discussed in a legal opinion

from the Department of Commerce’s

General Counsel, the Census Bureau

understands this term in accordance

with its ordinary meaning and the

overall purposes of Title 13. It is

important to note that even if Title 13

were silent as to the obligation to use

sampling if feasible, the Census Bureau

would apply criteria similar to those

described below to determine whether

to correct the census through the use of

statistical sampling. The Census Bureau

is committed to using reliable statistical

methods if those methods can be

expected to improve the overall

accuracy of the census.

The Definition of Feasibility

The Census Bureau’s determination

that sampling is ‘‘feasible’’ is based on

whether its use is possible, that is,

compatible with other aspects of the

census plan and with any statutory,

timing, and funding constraints. Equally

important, this determination is based

on whether the use of sampling is

expected to improve the overall

accuracy of census data by improving

overall coverage and reducing the

differential undercount. These two

components of the feasibility

determination represent operational

feasibility and technical feasibility. Can

the Census Bureau produce the

statistically corrected block-level

numbers by the April 1, 2001, statutory

deadline? Can the statistically corrected

counts be expected to improve the

overall accuracy of census data?

More specifically, in the context of

Census 2000, the use of statistical

sampling is feasible to correct the

census if the two components of

feasibility, operational and technical,

38380 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

14The Census Bureau’s FY 1998 Appropriations

Bill (P.L. 105–119) requires the Census Bureau,

when it releases redistricting numbers based on

statistical methods, to also release data produced

without the use of statistical methods at all levels

of geography.

15Bureau of the Census, ‘‘Master Activity

Schedule for Census 2000.’’

16Sacramento, California; Menominee County,

Wisconsin; and Columbia, South Carolina and 11

surrounding counties.

are satisfied. Operational feasibility

refers to the Census Bureau’s ability to

conduct the A.C.E. with available

resources and within required deadlines

or time frames. Technical feasibility

refers to the Census Bureau’s

expectation that the A.C.E. statistical

methodology, if carried out as planned,

will improve the accuracy of the census

for non-apportionment uses of the data.

As discussed below, the Census

Bureau’s extensive experience with

coverage measurement surveys,

including its incorporation of

improvements since 1990, confirms the

conclusion that the A.C.E. is both

operationally and technically feasible.

Operational Feasibility

Operational feasibility refers to the

Census Bureau’s ability to conduct each

major component of the census within

applicable deadlines and with available

resources. The Census Bureau expects to

conduct each major component of the

census, including the A.C.E., in time to

meet the April 1, 2001, deadline for

producing the redistricting data.

Release of Data Products for Use in

Redistricting

The Census Bureau’s goal is to

produce the most accurate numbers

possible within the constraints imposed

by the federal statute and available

resources. Section 141(c) of Title 13

requires the Census Bureau to deliver

redistricting numbers to the states by

April 1, 2001.14 In past decennial

censuses, the Census Bureau has been

able to release redistricting numbers to

certain states prior to the federal

deadline, enabling redistricting officials

in those states to meet deadlines set by

state statutes and constitutions. The

Census Bureau will, as in the past,

release the numbers from Census 2000

to the states as they are ready, giving

priority to states that need to meet early

deadlines.

Operational Considerations

The Census Bureau’s detailed plan for

carrying out the entirety of the census

operation, including the A.C.E., is set

forth in the ‘‘Master Activity Schedule’’

(MAS).15 This plan has undergone

thorough reviews and analyses and

supports the Census Bureau’s

confidence that it can implement the

A.C.E. methodology correctly and

successfully. The Census Bureau

introduced its original Census 2000 plan

in 1995. Since that time, the plan has

been refined to incorporate testing,

analysis, expert and other public input,

and policy and programmatic changes,

including the Supreme Court’s January

25, 1999, ruling. During the last five

years, the Census Bureau has put into

place a comprehensive project

management framework based on a

powerful project management tool used

by some of the world’s largest private

organizations. The use of this and other

project tools, such as an integrated cost

model and function and process

modeling software, led to the Census

Bureau’s determination that it could

produce the statistically corrected

numbers by April 1, 2001. A revised

Census 2000 MAS, reflecting this

determination, along with the Census

2000 Operational Plan, were presented

to the U.S. House of Representatives

Subcommittee on the Census, as well as

the Census Bureau’s other oversight and

appropriations committees and

subcommittees, in March 1999.

Resource Considerations

Resources are also relevant to a

feasibility determination. Based on

current FY 2000 appropriations and the

anticipation that the Administration’s

FY 2001 budget request for Census 2000

will be appropriated, the Census Bureau

should be able to hire sufficient staff

and acquire the necessary equipment to

complete Census 2000 and produce

statistically corrected redistricting

numbers by the April 1, 2001, statutory

deadline.

The Census 2000 Dress Rehearsal

In preparing for Census 2000, the

Census Bureau, as has been its practice

for many decades, conducted a dress

rehearsal, or full-scale census

simulation, in several sites across the

country.16 The dress rehearsal

demonstrated the operational feasibility

of producing the statistically corrected

block-level data by the statutory

deadline. The Census Bureau was able

to produce data without the use of

statistical sampling within nine months

(as it is required to do for

apportionment) and statistically

corrected data within 12 months (as it

is required to do for redistricting).

Technical Feasibility

Technical feasibility refers to whether

the statistical methodology used by the

A.C.E. will improve accuracy.

Measuring the accuracy of the census is

not a simple task. There are two types

of accuracy—numeric and distributive—

central to census operations and the

uses of census data. Starting with the

planning for the 1980 census, the

Census Bureau has developed, tested,

refined, and implemented statistical

methods to improve both the numeric

and distributive accuracy of the census

enumeration, culminating in the 2000

A.C.E. design. The Census Bureau

expects the A.C.E. to improve both

numeric and distributive accuracy.

Defining Numeric and Distributive

Accuracy

In analyzing the effect of the A.C.E. on

accuracy, this discussion focuses on the

accuracy of population totals for

geographic areas and demographic

groups, and, though important in the

overall understanding of the census, not

on the accuracy of detailed

characteristic data for people or housing

units.

Numeric accuracy refers to how close

the overall count of a particular

geographic area or demographic group is

to the ‘‘truth,’’ that is, to the actual

number of people who reside in that

area or belong to that group. Distributive

accuracy refers to how close the relative

proportion or share of a geographic area

or demographic group is to its true share

relative to other areas or groups. A

census operation that increases numeric

accuracy moves the overall count for

any particular area or demographic

group closer to the true total. For

example, an operation that enumerates

individuals in a particular state who

would otherwise be missed, increases

the numeric accuracy of that state. A

census operation that increases

distributive accuracy will improve the

accuracy of the population share for a

given area or demographic group

compared to other areas or demographic

groups ‘‘ in other words, improve the

accuracy of the estimated proportions or

shares of the total population for the

areas or groups.

A perfect census—one in which every

resident is counted once and only once

and is correctly located—would be both

numerically and distributively accurate.

But, as noted above, the Census

Bureau’s experience leads it to expect

that, absent statistical correction,

Census 2000 will result in both a net

national undercount and various

differential undercounts. Such

undercounts affect both numeric and

distributive accuracy. Although much of

the analysis of the 1990 census focused

on distributive accuracy, both types of

accuracy are important and must be

considered in designing a census that

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38381

17 In this program, local and tribal governments

liaisons in mailout/mailback areas review the

Census Bureau’s address list for their areas and

provide the agency with the addresses of all newly

constructed housing units as of April 1, 2000. The

Census Bureau matches these addresses to its

address list, updated with United States Postal

Service files, and verifies and enumerates those

addresses that are not on its address list.

will provide the most accurate count

possible.

Importance of and Relationship

Between the Two Types of Accuracy

The decennial census can be viewed

as one of the nation’s most important

civic ceremonies. Viewed in this broad

perspective, securing maximum

participation must be a key Census

Bureau goal. To the extent that the

census has the obligation to fully reflect

who Americans are and how they live,

everyone should be counted. Census

operations that improve numeric

accuracy, irrespective of their impact on

distributive accuracy, meet this most

basic goal.

In contrast, census operations that

improved distributive accuracy but left

many residents out of the count would

not meet this basic goal. For example, a

census that counted 90 percent of every

demographic group in every geographic

area would be distributively accurate,

but would fail the obligation of the

census to include everyone.

Numeric accuracy of census data is

particularly important when population

thresholds determine eligibility for

program funding. For example, in FY

1998, the U.S. Department of Housing

and Urban Development obligated over

$3 billion under its Community

Development Block Grants Entitlement

Program. For this program, the

population thresholds used are central

cities of metropolitan statistical areas;

other cities over 50,000 in metropolitan

statistical areas; and qualified urban

counties of at least 200,000 (excluding

the population in entitlement cities

located within the boundaries of such

counties). Central city and metropolitan

statistical area designations themselves

depend upon certain population

thresholds.

Additional uses of census data for

which numeric accuracy is critical are

associated with the Census Bureau’s

intercensal population estimates and

survey controls. Decennial census data

are the base for the Census Bureau’s

intercensal population estimates and

projections programs, programs that

produce annual population estimates for

all general purpose governments and

projections for the nation and states,

respectively. Specific uses of the

population estimates that depend on

numeric accuracy include use of the

estimates as controls for many federal

surveys, including the Current

Population Survey (which provides

monthly labor force and employment

data), and as denominators for many

critical federal data series, such as birth,

mortality, and cancer rates, as well as

per capita income.

For the purpose of reapportioning

seats in the House of Representatives,

distributive accuracy becomes a

principal concern, because

reapportionment is based on a

proportionate allocation formula.

Federal and state redistricting are based

on criteria for dividing state populations

into districts of equal size; thus both

numeric and distributive accuracy are

important. Distributive accuracy is also

central to federal funding allocations

that distribute funds based on relative

percentage of the population.

The goal of the Census Bureau is to

conduct a census that is both

numerically and distributively accurate.

This said, it is numeric accuracy that

drives the process for designing Census

2000 operations other than the A.C.E.

When it designs a decennial census, the

Census Bureau has available a very large

number of possible operations. It

assesses these operations against such

criteria as cost, statutory deadlines,

whether the staff necessary to

implement these operations can be

recruited and adequately trained, and

how well the operations fit with other

operations under consideration. In this

extensive process of evaluating

individual operations and then

assembling them in the final design,

there is one paramount criterion: what

census design has the highest

probability of correctly enumerating the

population? That is, can an operation

considered separately, and when

combined with other operations, be

expected to help the Census Bureau

correctly count as many people as

possible, given funding, timing, and

other constraints?

Obviously, if perfect numeric

accuracy were achieved for all

geographic areas and demographic

groups, then perfect distributive

accuracy would also result. However,

because it is difficult and perhaps

impossible to know a priori the effects

of a particular census operation on

distributive accuracy, assessing an

operation’s effect on distributive

accuracy can rarely be part of the

planning process. The difficulty of

designing operations for distributive

accuracy is compounded if it is to be

achieved across geographic areas and

multiple demographic groups and then

simultaneously across many levels of

geography. For example, the Local

Update of Census Addresses program,

being voluntary, may have benefitted

communities with strong local planning

departments more than other

communities. This program, then, had

an unpredictable effect on distributive

accuracy.

In principle, any given census

operation designed to increase numeric

accuracy can increase distributive

accuracy, leave it the same, or make it

worse. But in assembling a census

design, the Census Bureau does not

reject operations that would improve

numeric accuracy (and meet other

criteria for inclusion) even though such

operations might affect distributive

accuracy negatively, or indeterminately.

For example, the Census Bureau has

developed for Census 2000 an extensive

partnership program to assist local

jurisdictions and community

organizations in promoting participation

in the census. But increasing the counts

for these participating localities will not

necessarily translate into improvements

in distributive accuracy. If one state

promotes the census more effectively

than another state, the state with the

better promotion program may earn a

higher share of the total national

population than would otherwise be the

case.

Although the Census Bureau has

largely targeted its coverage

improvement programs in the areas that

have been the most difficult to count, it

has not rejected census operations that

might disproportionately improve the

count for groups that are already well

counted. An example of the latter in

Census 2000 is the ‘‘New Construction’’

program.17 Moreover, the Census

Bureau has supported the efforts of

neighborhoods, cities, and states to

increase the accuracy of their census

counts, irrespective of the effect on

distributive accuracy. The Census

Bureau views these increases in

numeric accuracy, even for well

counted groups, as important to the

most basic goal of the census—counting

everyone.

Finally, although different uses of

census data depend to varying degrees

on each type of accuracy, the two

concepts are related. When the census

falls short of overall numeric accuracy,

states and localities with large

populations that are differentially

undercounted will suffer a diminution

in proportionate shares. For example,

the differential undercount in the 1990

census caused states and localities with

large minority populations to suffer a

diminution in share. The Census Bureau

can and does try to improve both

38382 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

18This conclusion is based on the assumption

that the coverage improvement programs used for

Census 2000 will have similar results as those used

in 1990.

19Bureau of the Census, ‘‘Report to Congress—

The Plan for Census 2000,’’ 44–46. Census tracts are

small, homogeneous, relatively permanent

statistical subdivisions of counties formed for the

purpose of collecting and tabulating decennial

census data. Tracts typically contain between 1,000

and 8,000 people.

20When apportionment is calculated based on

Census 2000 counts, the average Congressional

District is expected to be over 600,000 people.

21The Census Bureau first used sampling in a

decennial census in 1940, in the program now

known as ‘‘long form’’ enumeration, which is used

to obtain detailed demographic information. The

Census Bureau has used sampling to conduct

federal surveys to collect key information,

including unemployment and labor force data, etc.,

for many decades.

22 J.G. Robinson and others, ‘‘Estimates of

Population Coverage in the 1990 United States

Census Based on Demographic Analysis,’’ Journal

of the American Statistical Association 88

(September 1993): 1061–77.

23For a detailed discussion of the 1980 Census

Post Enumeration Program, see Robert E. Fay and

others, The Coverage of Population in the 1980

Census (Washington, D.C.: Government Printing

Office, 1988), 37–92.

24 Department of Commerce, ‘‘Position on

Adjustment of the 1980 Census Counts for

Underenumeration,’’ Federal Register (16 December

1980) vol. 45, no. 243, p. 82872.

numeric and distributive accuracy by

bringing the total count for each area or

demographic group closer to its true

count.

Impact of the A.C.E. on Accuracy

The preceding discussion of accuracy

included a discussion of the design of

the census for apportionment purposes,

but did not consider the effects of the

A.C.E. on numeric and distributive

accuracy. As discussed below, the

A.C.E. measures and corrects for the

deficiencies in the initial census, and

consequently the Census Bureau expects

that the A.C.E. will improve both

distributive and numeric accuracy.

Based on decades of research

identifying and measuring the

undercount, as well as the 1990 census

evaluations (discussed below), the

Census Bureau expects the differential

undercount to persist in Census 2000,

with properties similar to those

measured in 1990.18 This extensive

research into measuring and correcting

the differential undercount, augmented

by enhancements to prior coverage

measurement surveys, leads the Census

Bureau to expect that the A.C.E. will

improve accuracy. The A.C.E. is

expected to improve numeric accuracy

by moving total counts closer to the true

count and to improve distributive

accuracy by more accurately counting

areas that contain significant

populations of historically

undercounted groups.

It is important to consider the

contribution of the A.C.E. to numeric

and distributive accuracy at different

levels of geography. The Census Bureau

expects that the A.C.E. will, on average,

improve numeric accuracy for

geographic areas down to and including

census tracts.19 ‘‘On average’’ means

that, while some tracts will be more

numerically accurate using uncorrected

numbers and others more accurate using

corrected numbers, the average effect

over all tracts is greater accuracy with

than without the A.C.E. The Census

Bureau also expects that improvement

will be greatest for those areas that

contain groups that have been

historically undercounted.

Regarding distributive accuracy, the

Census Bureau’s extensive evaluations

following the 1990 census led it to

conclude that the 1990 PES would have,

on average, increased distributive

accuracy for larger geographic areas,

including states and cities and counties

with more than 100,000 people. These

evaluations did not determine whether

the 1990 PES would have improved the

distributive accuracy of smaller

geographic areas.20 In addition, these

evaluations did not address whether the

unadjusted counts were more accurate

for these areas. The research on these

issues conducted by the Census

Bureau’s Committee on Adjustment of

Postcensal Estimates (CAPE) is

discussed more fully below. Based on

this research, the Census Bureau expects

the incorporation of the A.C.E. results in

the Census 2000 counts to have a

similar effect, that is, to improve

distributive accuracy for larger

geographic areas, as in 1990.

Historical Experience With Coverage

Measurement Surveys Demonstrates

Feasibility

The Census Bureau has a

longstanding practice of employing

scientific sampling techniques in the

decennial census whenever sampling

has the potential to lower costs without

negatively affecting quality.21 It has

devoted substantial resources for over

two decades to the development of

coverage measurement programs

employing high quality sampling

methodologies that enable the

production of more accurate data. The

feasibility assessment discussed in this

document is one more logical step along

that continuum.

The Census Bureau and leading

professional statistical organizations

have concluded that the best way to

address the persistent problems of the

undercount and the differential

undercount is to complement traditional

enumeration procedures with scientific

sampling, using DSE. Extensive

research, testing, and refinement of the

tools of statistical adjustment have led

the Census Bureau to determine that the

A.C.E. will improve the overall accuracy

of the census.

The Census Bureau also has used

Demographic Analysis to evaluate

coverage in decennial censuses and

broadly validate the coverage

measurement survey results.22 Since

independent Demographic Analysis

estimates are not available below the

national level, nor have estimates been

available for detailed demographic

groups (for example, tenure or detailed

racial groups), the Demographic

Analysis method has not been used to

adjust the census for undercoverage.

The 1980 Census Experience

Development of the modern coverage

measurement survey began with the

1980 Post Enumeration Program, or

PEP.23 The PEP was a coverage

measurement survey, based on DSE

methodologies, designed to evaluate the

accuracy of the 1980 census. Over 50

lawsuits were filed regarding the 1980

census, most contending that the results

of the PEP should have been used to

adjust the census. However, the PEP had

been designed primarily as a coverage

evaluation tool, rather than an

adjustment mechanism, making its use

to correct the census results

problematic. The Director of the Census

decided not to adopt the numbers

produced from this first attempt at

statistical correction using DSE, judging

the estimates to be flawed by missing

and inaccurate data.24

Significantly, however, the PEP

operation provided a wealth of

information on measuring coverage in a

census using DSE. The PEP illustrated

the potential use of coverage

measurement surveys as a coverage

evaluation tool for U.S. censuses. It was

clear in principle that coverage

measurement surveys could be used to

correct the census. In the two

subsequent decades, the Census Bureau

built upon the knowledge and

experience gained in the 1980 census.

Early Research and Development for the

1990 Census

After the 1980 experience, the Census

Bureau began an extensive review of its

coverage measurement program to

enhance the methods that had been

used in 1980 and to determine the

feasibility of a statistical adjustment in

1990. Adjustment of the census was a

topic of lively debate in the statistical

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38383

25See Tommy Wright and Joyce Farmer, ‘‘A

Bibliography of Selected Statistical Methods and

Development Related to Census 2000,’’ 3rd ed., 1

May 2000, for a list of many of the most significant

of these papers.

26 Dan Childers and others, ‘‘The Technical

Feasibility of Correcting the 1990 Census,’’ in

Proceedings of the Social Statistics Section of the

American Statistical Association Held in San

Francisco, California, 17–20 August 1987.

27 Dan Childers and Howard Hogan, ‘‘The 1988

Post Enumeration Survey Methods and Preliminary

Results,’’ in Proceedings of the Survey Research

Methods Section of the American Statistical

Association Held in New Orleans, Louisiana, 22–25

August 1988.

28Prior to the Department’s 1987 decision halting

the Census Bureau’s adjustment-related planning

activities for the 1990 census, the agency had

planned to conduct a PES of 300,000 housing units.

Under the terms of the stipulation, the Census

Bureau agreed to conduct a PES of approximately

165,000 housing units, the results of which could

be used to adjust the census.

29 Department of Commerce, ‘‘Final Guidelines

for Considering Whether or Not Statistical

Adjustments of the 1990 Decennial Census of

Population and Housing Should be Made for

Coverage Deficiencies of the Population,’’ Federal

Register (15 March 1990) vol. 55, p. 9838.

30Hogan, ‘‘1990 Post-Enumeration Survey,’’ 1054.

31Wright and Farmer, ‘‘A Bibliography of

Selected Statistical Methods Related to Census

2000.’’

32 Department of Commerce, ‘‘Adjustment of the

1990 Census for Overcounts and Undercounts of

Population and Housing: Notice of Final Decision,’’

Federal Register (22 July 1991) vol. 56, p. 33583.

33City of New York v. U.S. Dept. of Commerce,

822 F. Supp. 906, 928 (E.D.N.Y. 1993).

34 822 F. Supp. 906 at 918, fn. 27.

community during the 1980s. Census

Bureau professionals and outside

statisticians published more than 100

papers on coverage measurement

issues.25 In 1983, the Census Bureau

formed the Undercount Research Staff,

a staff of agency professionals charged

with addressing coverage measurement

issues and with assessing the potential

correction of the 1990 census. This

group conducted research over the

decade leading up to the 1990 census.

Planning for the 1990 census

progressed with a two-track approach—

preparing to take the best traditional

enumeration possible, while

simultaneously developing a PostEnumeration Survey (PES), a coverage

measurement survey the results of

which could be used to statistically

correct the census. The Census Bureau’s

position was that it would proceed with

correction if it could determine, prior to

the spring of 1987, that implementation

of a PES-based correction was feasible.

As part of its research effort, the Census

Bureau carried out the Test of

Adjustment Related Operations (TARO)

in 1986. Based on the results of the

TARO, as well as various theoretical

and empirical studies conducted since

1980, senior statisticians at the Census

Bureau concluded that statistical

methods existed that could produce

census counts with a reduced

differential undercount, and that if

funded and successfully completed, the

program incorporating these methods

could be used to statistically correct the

1990 census.26

As discussed below, the Department

of Commerce overruled the Census

Bureau and decided not to allow

adjustment of the 1990 census. The

Census Bureau’s research on the PES as

a coverage measurement tool continued,

including the conduct of the 1988 dress

rehearsal Post-Enumeration Survey. The

1988 dress rehearsal demonstrated

significantly improved operations and

once again demonstrated DSE’s

consistent ability to measure the

undercount and the differential

undercount.27

Litigation Challenging Decision to Halt

1990 Adjustment-Related Planning

Activities

The Department of Commerce, in the

fall of 1987, directed the Census Bureau

not to proceed with its plans to produce

adjusted census figures, prompting the

filing of a lawsuit against the

Department and the Census Bureau. As

part of that lawsuit, on July 17, 1989,

the Department of Commerce entered

into a stipulation, vacating the

Department’s 1987 decision against

adjustment and requiring the Secretary

to consider de novo, after the

completion of the census, whether

adjustment was warranted. The Census

Bureau would conduct a PES and

certain other adjustment-related

planning operations, 28 and the

Secretary was to announce his decision

on the adjustment issue by July 15,

1991. Pursuant to the stipulation, the

Department of Commerce agreed to

develop and adopt promptly

‘‘guidelines articulating what

defendants believe are the relevant

technical and nontechnical statistical

and policy grounds for the decision on

whether to adjust the 1990 Decennial

Census population counts.’’ An

adjustment would be made if the

Secretary of Commerce, in his judgment,

determined that doing so would satisfy

the guidelines. The stipulation also set

up a Special Advisory Panel composed

of four experts chosen by the plaintiffs

and four experts chosen by the

defendants; the Panel’s role was to

advise the Secretary regarding

adjustment. At this time, the Census

Bureau convened the Undercount

Steering Committee, a group of senior

career agency employees, and charged

the committee with evaluating the

conduct of the 1990 PES and assessing

the accuracy of the adjusted versus the

unadjusted census counts.

The Department of Commerce

published its final guidelines on March

15, 1990. 29 The guidelines established,

among other things, the principle that

the unadjusted census counts would be

presumed more accurate unless it could

be shown that the adjusted counts were

more accurate at the national, state, and

local levels. This presumption and the

guidelines in general will be discussed

in greater detail below.

Conducting the 1990 Census and

Deciding Against Adjustment

The Census Bureau applied the DSE

methodology in the 1990 PES to

produce a second set of population

counts for every block in the nation. 30

Under the direction of the Undercount

Steering Committee the Census Bureau

analyzed the PES results extensively,

producing 33 separate and detailed

technical reports analyzing various

aspects of the survey and its results. The

Census Bureau’s extensive analysis was

complemented by a large volume of

outside expert analysis of the PES

results. 31

Based on the Census Bureau’s

analyses, then Census Bureau Director

Barbara Bryant and the majority of the

Undercount Steering Committee

recommended that the 1990 census be

statistically adjusted. The Special

Advisory Panel, convened as part of the

stipulation, was divided in its

recommendations regarding adjustment.

The panel members selected by

defendants all recommended against

statistical adjustment, and the panel

members selected by the plaintiffs all

recommended in favor of adjustment.

On July 15, 1991, Secretary Mosbacher

announced that the 1990 decennial

census would not be statistically

adjusted. 32

After the Secretary announced his

decision, the plaintiffs returned to court,

seeking an order compelling the

Department to adjust the 1990 census.

On April 13, 1993, Judge McLaughlin of

the U.S. District Court upheld Secretary

Mosbacher’s decision, determining that

the decision was not arbitrary or

capricious, although he stated that

‘‘were this Court called upon to decide

this issue de novo, I would probably

have ordered the adjustment.’’ 33 Judge

McLaughlin noted also that ‘‘light of

recent improvement in statistical tools

and the practical benefits that the 1990

PES has provided, the use of adjustment

in the next census is probably

inevitable.’’ 34

38384 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

35 Department of Commerce, ‘‘Adjustment of the

1990 Census,’’ 33582.

36CAPE; ‘‘Additional Research on Accuracy of

Adjusted Versus Unadjusted Census Base for Use in

Intercensal Estimates,’’ Addendum to Report of the

Committee on Adjustment of Postcensal Estimates,

25 November 1992, referred to later as CAPE

Addendum.

37As will be discussed more fully below, more

recent research has confirmed that the Census

Bureau similarly cannot determine that the

uncorrected 1990 data were more distributively

accurate. For aggregations below 100,000, the

evidence as to accuracy is indeterminate, that is,

neither favoring the unadjusted nor the adjusted

counts. See Bureau of the Census, ‘‘Analysis of

CAPE Findings on PES Accuracy at Various

Geographic Levels,’’ by Sally M. Obenski and

Robert E. Fay, 9 June 2000.

38 Department of Commerce, ‘‘Decision of the

Director of the Bureau of the Census on Whether to

Use Information from the 1990 Post Enumeration

Survey (PES) to Adjust the Base for the Intercensal

Population Estimates Produced by the Bureau of the

Census,’’ Federal Register (4 January 1993) vol. 58,

no. 1, 69.

39 Ibid., 70.

40 Katharine G. Abraham, U. S. Bureau of Labor

Statistics, to Harry A. Scarr, U. S. Bureau of the

Census, 1 December 1993.

41 Ibid.

42 General Accounting Office, Decennial Census:

1990 Results Show Need for Fundamental Reform,

Report to Congressional Requesters, 9 June 1992,

62, 49 GAO/GGD–92–94.

43Congress, House, Decennial Census

Improvement Act of 1991, 102nd Cong., 2nd sess.,

H.R. 3280, Congressional Record, daily ed. (9

October 1991), H7694 became Public Law 102–135

on October 24, 1991. It was set forth in the

commentary to Title 13, U.S. Code, sec. 141.

44 Duane L. Steffey and Norman A. Bradburn,

Counting People in the Information Age

(Washington, D.C.: National Academy Press, 1994),

4.

Postcensal Estimates and Survey

Controls Decision

Although Secretary Mosbacher

determined not to adjust the 1990

census for estimated net census

undercount, he deemed it appropriate

that the Census Bureau consider using

the adjusted counts as the basis for

producing postcensal estimates: ‘‘I am

today requesting that the Census Bureau

incorporate, as appropriate, information

gleaned from the Post-Enumeration

Survey into its intercensal estimates of

the population.’’ 35

Census Bureau Director Bryant

convened the Committee on Adjustment

of Postcensal Estimates (CAPE) to study

this issue and make recommendations

to her. CAPE was a group of senior

statisticians, demographers, and other

Census Bureau professionals assembled

to conduct additional analyses of the

adjusted counts. The Committee’s work

extended over a 15-month period. The

Committee issued a report on August 8,

1992, and an Addendum on November

24, 1992. 36 The Addendum was the

result of continuing and more focused

analysis by the team. Taken together,

the initial CAPE report and the

Addendum found that the adjusted

numbers were overall more accurate in

terms of distributive accuracy at the

state level and for areas with greater

than 100,000 population. For areas with

populations of less than 100,000, the

CAPE could not identify any

improvement in distributive accuracy

for the adjusted data. 37

In January 1993, Dr. Bryant

announced that the Census Bureau

would not use the 1990 adjusted counts

as the basis for producing postcensal

estimates of the population. 38 Director

Bryant’s Census decision was made in

light of, though not explicitly governed

by, the litigation guidelines that stated

that adjustment was not warranted

unless improvement could be clearly

demonstrated down to small levels of

geography, such as places and counties.

Recognizing the improvements in

accuracy for certain uses of census data,

Dr. Bryant decided to offer sponsors of

federal sample surveys the option of

having their surveys calibrated to

population estimates benchmarked to

adjusted census results. 39 Accordingly,

in December of 1993, the Bureau of

Labor Statistics (BLS) requested that the

Census Bureau convert the Current

Population Survey controls to ones

based on estimates incorporating the

results of the 1990 PES. The BLS stated

its conviction ‘‘that the undercountadjusted estimates provide a more

accurate reflection of the level and

distribution of the national population

and that of most States than the

estimates based on the raw Census

counts.’’ 40 The BLS also requested that

the population controls for the

Consumer Expenditure Survey be

adjusted in a similar fashion. 41

Subsequent to the BLS decision, all

other major national household surveys

conducted by the Census Bureau for

other agencies of the federal statistical

system were converted to an adjusted

population basis. Thus, corrected data

from the 1990 census are already

incorporated in many federal statistical

series.

Early Census 2000 Planning

The results of the 1990 census led the

Census Bureau, other professional

statisticians, and Congress to conclude

that significant changes were required

for the next census. A comprehensive

re-examination of census methodology

was needed to identify a census design

that would improve the accuracy of the

census. To this end, in November 1990,

the Census Bureau established the

‘‘Task Force for Planning for the Year

2000 Census and Census-Related

Activities for 2000–2009.’’ The Task

Force was responsible for defining a

census design for Census 2000,

considering both policy and technical

issues, and a demographic measurement

system for related activities for 2000

through 2009.

In June 1992, the General Accounting

Office (GAO) released a comprehensive

evaluation of the 1990 census,

discussing lessons learned and

identifying opportunities for

fundamental, effective reforms. The

GAO concluded that reduced data

quality (including failure to make

reductions in the net and differential

undercounts)’’ * * * is a cost of the

current approach to taking the

census * * *’’ and that ‘‘[t]he results

from 1990 demonstrate that adding

more resources [while employing

traditional census-taking methods] is

unlikely to allow the Bureau to

enumerate that last remaining segment

of the population.’’ 42

Also at the beginning of the decade,

two panels of the National Academy of

Sciences’ (NAS) National Research

Council were convened to study ways to

improve the census for 2000. The

Decennial Census Improvement Act of

1991, signed into law by President

Bush, required the Census Bureau to

contract with the National Academy of

Sciences to study*** the means by

which the Government could achieve

the most accurate population count

possible * * *’’ specifically

considering, among other things, ’’. . .

the appropriateness of using sampling

methods in combination with basic

data-collection techniques or otherwise,

in the acquisition or refinement of

population data, including a review of

the accuracy of data for different levels

of geography * * *.’’ 43 The Panel on

Census Requirements in the Year 2000

and Beyond was established pursuant to

this statutory requirement,

supplementing the work already being

performed by the NAS Panel to Evaluate

Alternative Census Methods. This latter

panel was established to provide an

independent review of the technical and

operational feasibility of the design

alternatives and of the tests to be

conducted by the Census Bureau. The

Methods Panel’s recommendations on

testing and design alternatives informed

the final design of the original plan for

Census 2000. The Panel issued its final

report in 1994, recommending that the

agency use sampling as an essential part

of census-taking in Census 2000. 44

In June 1995, the Task Force

convened at the beginning of the decade

issued final recommendations in its

‘‘Global Report,’’ suggesting a number of

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38385

45Bureau of the Census, ‘‘Reinventing the

Census,’’ Global Report of the Task Force for

Planning the Year 2000 Census, June 1995.

46For a description of these methodologies and

the differences between them, see White and Rust,

Preparing for the 2000 Census: Interim Report II,

48–51.

47A third National Academy of Sciences panel,

the Panel to Evaluate Alternative Census

Methodologies, was convened to study ways to

improve the census for 2000. In its earlier report

(Andrew A. White and Keith F. Rust, eds.,

Sampling in the 2000 Census: Interim Report I

(Washington, D.C.: National Academy Press, 1996)

following the 1995 Census Test, but before all the

analyses from that test had been completed, the

Panel concluded that ’’* * * nothing in the [1995]

census test, nor any other development, suggests

that a decennial census that*** reduces

differential undercoverage can be conducted

without the use of some form . . . of sampling for

integrated coverage measurement’’ (pp. 2–3). Based

on the performance of DSE versus CensusPlus in

the 1995 Census Test, the Census Bureau selected

the former methodology for Census 2000, and the

Panel supported that decision (White and Rust,

Preparing for the 2000 Census: Interim Report II,

51–59).

48Edmonston and Schultze, Modernizing the U.S.

Census, 3.

49 Department of Commerce, ‘‘Census 2000 Dress

Rehearsal Shows Undercount Persists; Scientific

Methods Correct Race and Ethnic Differential,’’

Commerce News, 20 April 1999, CB99–CN.16

(revised).

50Bureau of the Census, ‘‘Some Results from the

Census 2000 Dress Rehearsal,’’ by Rajendra Singh,

DSSD Census 2000 Dress Rehearsal Memorandum

Series A–76, 26 February 1999, 6.

51A fourth NAS panel was convened in June 1998

to review the Census Bureau’s plans, procedures,

and operations in connection with the Dress

Rehearal and Census 2000. Experts from this panel

are examining, among other things, the statistical

methodology and procedures for the A.C.E.

52Cohen, White, and Rust, Measuring a Changing

Nation, 4.

53Edmonston and Schultze, Modernizing the U.S.

Census, 100.

54While support is widespread, the Census

Bureau does not mean to imply that there is

unanimous support on the issue. See, for example,

Lawrence D. Brown and others, ‘‘Statistical

Controversies in Census 2000,’’ Jurimetrics 39

(Summer 1999).

55Bureau of the Census, ‘‘Report to Congress—

The Plan for Census 2000,’’ 24–25; Joint Census

Advisory Committees on the Racial and Ethnic

Populations, ‘‘Recommendations Agreed Upon by

the Four Census Advisory Committees on the

African American, American Indian and Alaska

Native, Asian and Pacific Islander and Hispanic

Populations Made at the Meeting Held on May 22–

23, 1997,’’ Recommendation 3; the Secretary of

Commerce’s 2000 Census Advisory Committee,

‘‘Final Report, Recommendation 3B, Post

Enumeration Survey with a Traditional Census,’’ 22

January 1999; and Census Advisory Committee of

Professional Associations, ‘‘Recommendations

Made as a Result of the Meeting on April 22–23,

1999,’’ Recommendation 1.

improvements for Census 2000. 45 The

Task Force endorsed the Census

Bureau’s basic plan to conduct an

Integrated Coverage Measurement (ICM)

survey and suggested that the Census

Bureau pursue an ICM design that

would incorporate the best features of

alternative methodologies, including

DSE and CensusPlus. 46 The Census

Bureau tested these alternate

methodologies in the 1995 Census Test,

concluding along with the NAS Panel to

Evaluate Alternative Census

Methodologies that DSE offered the best

opportunity to produce high quality

statistical correction. 47

Also in that year, the Panel on Census

Requirements in the Year 2000 and

Beyond issued its final report. The

Panel recommended the use of sampling

and estimation techniques in Census

2000, concluding that:

It is fruitless to continue trying to count

every last person with traditional census

methods of physical enumeration * * *. It is

possible to improve the accuracy of the

census count with respect to its most

important attributes by supplementing a

reduced intensity of traditional enumeration

with statistical estimates of the number and

characteristics of those not directly

enumerated.48

The Census 2000 Dress Rehearsal

The Census Bureau conducted a dress

rehearsal in 1998 in several sites across

the country, an important opportunity

to test the DSE methodology in as near

a census-like environment as possible.

The Census Bureau concluded from the

dress rehearsal results that ‘‘[t]he data

showed across-the-board that the

undercount, which has been measured

in every census since 1940, persists

today, but that scientific methods used

at two of the three test sites corrected for

it.’’ 49 The dress rehearsal data also

displayed the persistence of the

differential undercount.50 In

Sacramento, the estimated undercount

rates that would have resulted without

the use of Integrated Coverage

Measurement were 4.7 percent for nonHispanic Whites, compared to 8.7

percent for African Americans, 8.3

percent for Hispanics, and 6.0 percent

for Asians. In Menominee County,

Wisconsin, which is largely composed

of the Menominee American Indian

Reservation, the estimated undercount

rate for non-Hispanic American Indians

that would have resulted without the

use of Integrated Coverage Measurement

was 4.1 percent. In the South Carolina

site, the estimated undercount rate for

non-Hispanic Whites was 6.3 percent

and 13.2 percent for all others

(Hispanic, Black, American Indian,

Hawaiian, and Asian).

It is clear from these results that,

based on traditional census-taking

methods alone, there was a substantial

net undercount in all three sites, as well

as a differential undercount of racial

and ethnic minorities in those

jurisdictions. The dress rehearsal

demonstrated the operational feasibility

of the A.C.E. and enhanced the Census

Bureau’s knowledge of the properties of

statistical correction.

External Review

The Census Bureau’s confidence that

the application of the DSE methodology

will result in a more accurate census is

shared by many other entities that have

critically examined this issue. Four

different NAS panels over the decade

have clearly endorsed the concept that

a properly designed and executed

coverage measurement survey has the

potential to produce a more accurate

census.51 In 1999, the NAS Panel to

Evaluate Alternative Census

Methodologies concluded that:

The only cost-effective methodology

available for measuring the degree of

differential undercoverage for subnational

areas is a large-scale post-enumeration survey

coupled with dual-system estimation * * *.

If the Supreme Court prohibits use of

integrated coverage measurement for

apportionment, the panel still strongly

supports a post-enumeration survey * * *

for purposes other than apportionment.52

This recent conclusion is in line with

those of the other three NAS panels. For

example, in 1995, the Panel on Census

Requirements in the Year 2000 and

Beyond concluded that use of a highquality survey in conjunction with the

2000 census will result in ‘‘* * *

improved accuracy with respect to the

count and differential undercount for

the nation as a whole as well as large

areas and groups.’’ 53

Numerous other organizations agree

that the use of a properly conducted

scientific survey in conjunction with the

enumeration has the potential to

produce a more accurate census in

2000.54 These include, among others,

the American Statistical Association,

the American Sociological Association,

the General Accounting Office, the

Inspector General of the Department of

Commerce, the Secretary of Commerce’s

Census 2000 Advisory Committee, the

Census Bureau’s Advisory Committee of

Professional Associations, and the

Census Bureau’s Race and Ethnic

Advisory Committees.55

A.C.E. Implementation Issues

The 1990 census coverage

measurement survey was one of the

most thoroughly evaluated programs

conducted by the Census Bureau. The

Census Bureau and other interested

parties have analyzed volumes of data

on the survey’s effects on accuracy and

how its results compared to the 1990

unadjusted census. Some of this

analysis was performed in conjunction

with Secretary Mosbacher’s 1991

decision and the 1992 Committee on

38386 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

56Wright and Farmer, ‘‘A Bibliography of

Selected Statistical Methods Related to Census

2000.’’

57Bureau of the Census, ‘‘An Analysis of the

Consistency of the 1990 Mosbacher Guidelines to

U.S. Census Bureau Standards,’’ by Sally M.

Obenski and Robert E. Fay, 16 May 2000.

58Obenski and Fay, ‘‘Analysis of CAPE Findings

on PES Accuracy’’; and Bureau of the Census,

‘‘Analysis of CAPE Findings on 1990 PES Technical

Issues,’’ by Sally M. Obenski, 9 June 2000.

59 Department of Commerce, ‘‘Adjustment of the

1990 Census,’’ 33583.

Adjustment of Postcensal Estimates

(CAPE) report, but the Census Bureau

has continued to examine the adjusted

and unadjusted census data from 1990.

These analyses have further clarified the

relationship between the adjusted and

the unadjusted 1990 census counts.

The extensive study of the 1990

coverage measurement survey identified

a number of issues. The Census Bureau

has considered these and other issues in

assessing the feasibility of statistically

correcting the Census 2000 counts. The

following discussion presents many of

these issues and addresses why the

Census Bureau expects the A.C.E. to

improve the overall accuracy of the

census. In addition, changes in the

A.C.E. design and their impact on

accuracy are discussed.

Measuring Accuracy

Measuring accuracy in both the

enumeration and the coverage

measurement survey involves

examining two types of error. One type,

sampling error or variance, arises from

the use of a sample to represent a

population. Sampling error will occur

only in the A.C.E. The other type, often

termed nonsampling error, represents

all other sources of error. Of particular

concern in nonsampling errors are

systematic errors or biases.

Nonsampling errors will occur in both

the initial census and the A.C.E. The

most serious source of bias in the initial

census is coverage error resulting from

people missed or erroneous

enumerations. The most notable

example of bias in the enumeration is

the historical phenomenon of the net

undercount, including the differential

undercount. Bias can also occur in the

A.C.E., including errors due to false

matches or nonmatches, inaccurately

accounting for missing information, and

other systematic collection or

processing errors.

In designing coverage measurement

surveys, the Census Bureau must strike

a balance between sampling variance

and bias. In comparing the accuracy of

the 1990 coverage measurement survey

to the accuracy of the unadjusted

census, the Census Bureau concluded

that the combined error in the coverage

measurement survey was lower than the

large bias in the census enumeration

and therefore recommended adjustment.

Secretary Mosbacher did not accept this

recommendation and explained his

reasons for not adjusting in his 1991

decision paper.

Assessment of Issues Emerging from

1990

The scrutiny and analysis of the 1990

census adjustment decision extended

and sharpened discussions in the

statistical community regarding the use

of a coverage measurement survey to

correct for census undercounts. Many of

these issues were the subject of

extensive discussion in Secretary

Mosbacher’s July 1991 decision

document and in the 1992 CAPE report.

Over the past decade, issues regarding

the use of sampling to correct the census

have been debated frequently in the

technical literature.56

Some of these issues primarily

address the basic principles and

theories that must be considered in

determining the proper application of a

coverage measurement survey and DSE.

For these issues reasoned judgment has

to be invoked, and it is difficult to

resolve these issues definitively by

quantitative measurements. For

example, what is the proper standard for

deciding whether the coverage

measurement survey should be used to

correct the census? What priority should

be given to numeric versus distributive

accuracy? What are plausible

assumptions about the distribution of

individuals who are missed by both the

initial census and the coverage

measurement survey?

Other issues focus more on how well

the Census Bureau can implement the

coverage measurement survey,

including the estimation processes. Is it

operationally feasible to conduct the

A.C.E. and produce the corrected results

within the decennial time frame? Are

the levels of sampling variance

associated with the A.C.E. estimates

reasonable? Can the levels of matching

or other processing errors that occur in

A.C.E. operations be kept to a

minimum? These issues, while still

subject to some degree of technical

judgement, can often be evaluated by an

examination of quantitative data.

As part of its comprehensive

assessment of the A.C.E. design, senior

Census Bureau officials requested a

careful analysis of the technical issues

identified in both the Mosbacher

document and the CAPE report in order

to ensure that cited concerns about

accuracy had been adequately

addressed. The Census Bureau’s

analysis of the Mosbacher document

focused on the Secretary’s guidelines

and on supporting evidence for his

decision.57 The Census Bureau’s

analyses of the CAPE report focused on

the accuracy of the unadjusted versus

the adjusted census counts for different

levels of geography and the status of the

technical issues introduced.58

In addition to the discussion of

technical issues, Secretary Mosbacher’s

analysis (and other reports critical of

sampling) introduced a number of nontechnical considerations. Secretary

Mosbacher, for example, opined that

‘‘adjustment would open the door to

political tampering with the census in

the future’’ 59—a theme frequently

repeated in political, though not in

scientific, discussions of sampling. No

evidence has been presented that the

Census Bureau has the competence to

assess how its selection or

implementation of census operations,

including the many technical

components of the A.C.E., might

predetermine partisan outcomes.

Furthermore, the highly pre-specified

A.C.E. procedures make Census 2000

highly resistant to any form of

manipulation. Although there are a

number of agencies and groups—

including the congressional committees

charged with oversight of Census 2000,

the General Accounting Office, the

Census Monitoring Board, the Inspector

General of the Department of

Commerce, numerous advisory

committees and other watchdog

efforts—scrutinizing the planning and

conduct of Census 2000, no evidence

has been presented suggesting that the

Census Bureau has any intention to

affect political outcomes, or, if it did,

that it has the technical ability to do so.

The Census Bureau disputes any and all

accusations that it would act out of

political motives, and in this document

restricts its discussion of concerns about

the A.C.E. to those with technical and

scientific content.

The Proper Standard To Use in

Deciding Whether to Statistically

Correct the Counts for NonApportionment Purposes

As was discussed earlier, Secretary

Mosbacher’s adjustment decision

regarding the 1990 census was

controlled by eight guidelines

promulgated in connection with

pending litigation. Secretary

Mosbacher’s decision not to adjust the

1990 census was based in large part on

the standard articulated in the first

guideline—that the unadjusted census

would be ‘‘* * * considered the most

accurate count of the population of the

United States, at the national, state, and

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38387

60 Ibid., 33593.

61 Ibid., 33592.

62 Ibid., 33584.

63CAPE, 21–23.

local level, unless an adjusted count is

shown to be more accurate.’’

Analysis and Response

This guideline assumed a priori that

the unadjusted census counts were

superior and required proof that the

adjusted counts were better in terms of

distributive accuracy at all three levels.

This decision guideline required the

adjusted counts to satisfy criteria that no

other census operation could meet—in

effect, the 1990 census coverage

measurement survey was subjected to a

higher standard than all other census

operations.

If the Census Bureau had historically

applied a similar presumption that a

change to the census operation must

demonstrate increased accuracy with

convincing evidence for small levels of

geography, it would not have made

many important changes in censustaking methodology. For example, such

a standard would not have permitted

the Census Bureau to replace 100-

percent in-home ‘‘personal’’ visits with

mail questionnaires in the 1970 census.

The Census Bureau did not know

whether this fundamental change to the

census operation would increase

accuracy at all levels. Nor, in 2000,

could the Census Bureau determine a

priori that extensive promotion and

paid advertising would increase

accuracy at all levels, or for that matter,

would be effective in all areas or for all

demographic groups. If applied to all

proposals to improve the initial census

counts, this standard would effectively

halt the Census Bureau’s long tradition

of scientific and technical innovation.

For Census 2000, the Census Bureau

will make the determination on whether

to use the A.C.E. to correct Census 2000

after evaluating (1) the conduct of key

operations, (2) the consistency of the

A.C.E. results with historical measures

of undercount, and (3) measures of

quality. As described previously, the

Census Bureau’s comprehensive

ongoing analyses and experience with

conducting coverage measurement

surveys have led it to expect that the

A.C.E. will improve overall numeric and

distributive accuracy and that it will

reduce the differential undercount.

Therefore, statistical correction is

appropriate absent strong evidence that

it will degrade the overall quality of the

final census data. However, the Census

Bureau will conduct an objective review

before making a final determination to

release the statistically corrected data.

The process that the Census Bureau will

follow in making this determination is

described in more detail at the end of

this document. The Census Bureau will

be documenting and discussing both

this process and the criteria on which

the determination will be made in a

public setting in the fall of 2000.

Numeric v. Distributive Accuracy

The 1990 census adjustment decision

(and the closely related decision on the

adjustment of the postcensal estimates)

was unequivocal in giving priority to

distributive over numeric accuracy.

Secretary Mosbacher interpreted the

Constitutional and legal purposes of the

census to require that:

* * * accuracy should be defined

predominately in terms of getting the

proportional distribution of the population

right among geographic and political units.

This argues for putting aside the judgment of

accuracy based on getting absolute numbers

right (numeric accuracy) and instead

focusing on the question of whether there is

convincing evidence that the accuracy of

population distribution in the adjusted

numbers (distributive accuracy) is superior to

the distributive accuracy of the actual

enumeration.60

This injunction, when joined with the

standard in the first guideline, requires

not only that the adjusted counts be

demonstrably more accurate at very low

levels of geography but that they be

more distributively accurate at those

levels. This emphasis was reflected in

many of the technical papers that have

been written on the 1990 census.

Comparatively less attention has been

directed to the importance of numeric

accuracy, despite the importance that

the Census Bureau attaches to it. In fact,

Secretary Mosbacher critiqued the

Census Bureau for its interpretation ‘‘of

accuracy as concerned with getting the

number of people closer to the truth

rather than getting the allocation of the

population for the purposes of political

representation and funding closer to the

truth.’’ 61

Analysis and Response

The Census Bureau believes that the

adjustment decision in 1990 did not

adequately consider the improvements

to numeric accuracy that can result from

statistical correction. Numeric and

distributive accuracy are discussed

more fully above. The issue here is the

relative importance that should be

assigned to numeric and distributive

accuracy in assessing the results of the

coverage measurement survey.

Judgments can differ on this issue. It is

the strong judgment of the Census

Bureau that in deciding whether to use

a coverage measurement survey to

improve the census, both numeric and

distributive accuracy should be taken

into account.

The analysis and decision in 1990

focused almost exclusively on

distributive accuracy. Although

Secretary Mosbacher stated that the

Census Bureau had provided substantial

evidence (although ‘‘not necessarily

convincing’’) that the adjusted counts

were more numerically accurate, he

based his conclusion not to adjust

partially on the fact that improvements

to distributive accuracy could not be

demonstrated by convincing evidence at

national, state, and local levels.62 Given

the decision criteria introduced by

Secretary Mosbacher, the CAPE also

focused on distributive accuracy.

The interaction between numeric and

distributive accuracy is quite

complicated, but must be considered in

the analysis of the two types of

accuracy. Clearly, there are situations

where gains in numeric accuracy are

expected without improvement in

distributive accuracy. For areas or

groups that have similar undercount

rates, improvements to numeric

accuracy are expected from the A.C.E.

corrections. However, the distributive

accuracy of these areas will be

unchanged by the correction, because

they will experience similar corrections.

This outcome is expected, because gains

in distributive accuracy are realized

when areas corrected for significant

undercounts are compared with areas

that have little undercount. Because the

A.C.E. is designed to improve the

numeric accuracy of areas with

significant undercounts, the Census

Bureau expects that the A.C.E. will

improve both numeric and distributive

accuracy and thus result in a more

accurate census overall.

Correlation Bias

Correlation bias is the result of either

lack of independence between the

initial census and the coverage

measurement survey, or of variable

inclusion probabilities within a poststratum.63 Frequently, the term is used

to refer to error caused by individuals

systematically missed in both the initial

census and the coverage measurement

survey. Important assumptions for DSE

are that everyone in a given poststratum has a similar inclusion

probability and that the census and the

coverage measurement survey are

independent. Technically, these

assumptions are referred to as

homogeneity and causal independence,

respectively. Correlation bias occurs

when these assumptions are not fully

satisfied. Although it is theoretically

possible for correlation bias to result in

38388 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

64 Department of Commerce, ‘‘Adjustment of the

1990 Census,’’ 33591–92.

65 Ibid.

66William R. Bell, ‘‘Using Information from

Demographic Analysis in Post-Enumeration Survey

Estimation,’’ Journal of the American Statistical

Association 88 (September 1993): 1106–1118; and

Bureau of the Census, ‘‘Report of the Working

Group on the Use of Demographic Analysis in

Census 2000,’’ by William R. Bell and others, 6 May

1996.

67CAPE, Table 2, Attachment 3A.

68Bureau of the Census, ‘‘Technical Assessment

of the Accuracy of Unadjusted Versus Adjusted

1990 Census Counts,’’ Report of the Undercount

Steering Committee, 21 June 1991, p. 2; and CAPE,

1.

69CAPE Addendum.

either underestimation or

overestimation by DSE, it is generally

expected that correlation bias leads to

underestimation. This will be the case,

for example, when there are individuals

who have little or no chance of being

included in either the initial census or

the coverage measurement survey. Some

critics of the 1990 coverage

measurement survey were concerned

that correlation bias was so large as to

preclude an improvement in

distributive accuracy from adjustment.64

Analysis and Response

Correlation bias exists and will affect

all dual system estimates. Poststratification is used to minimize

correlation bias. However, poststratification is not a perfect solution,

and it is reasonable to presume that

some heterogeneity or causal

dependence will persist, leading to

some correlation bias. Comparisons

with Demographic Analysis, though

subject to limitations, have been used to

obtain indications of possible

correlation bias at the national level by

age-sex-race groups. These comparisons

in 1990 suggested correlation bias for

adult Black males, and gave much less

or no evidence of correlation bias for

other groups. These analyses were

restricted to the national level, and gave

no indication of how any persons

reflected in correlation bias may have

been distributed geographically. In fact,

there are no empirical data that can be

used to definitely measure correlation

bias below the national level. As a

result, different hypotheses have been

set forth regarding whether the A.C.E.

will improve accuracy, particularly

distributive accuracy. In the absence of

quantitative data, the issues regarding

the effects of correlation bias can only

be resolved by a review of the

assumptions underlying the various

hypotheses, and by making judgments

regarding which assumptions are more

plausible.

The uncertainty about the geographic

distribution of persons reflected in

correlation bias relates to a concern of

Secretary Mosbacher—the concern that

because the distribution of those people

missed by both the census and the

coverage survey was not known, it

could not be demonstrated that a

statistical correction would improve

distributive accuracy.65 However, such

a concern implicitly assumes that the

distribution of correlation bias in dual

system estimates differs from the

distribution of undercount, as estimated

in A.C.E. While recognizing the inherent

limitations of its knowledge about the

distribution of correlation bias, the

Census Bureau believes it is more

plausible to assume that correlation bias

will tend to be distributed in a positive

relation to the distribution of estimated

undercount rates. A range of models

reflecting plausible assumptions for the

distribution of correlation bias have

been analyzed.66 This analysis of

correlation bias, based on plausible

assumptions, leads the Census Bureau

to expect that improvements in

distributive accuracy will be achieved

by a properly designed and conducted

coverage measurement survey.

Potential effects of correlation bias on

numeric accuracy can also be addressed.

Correlation bias, when present, is

generally expected to lead to

underestimation by dual system

estimates. Therefore, when the DSE

estimates an undercount in the initial

census, by implication the initial census

counts are even more severely

undercounted. So the statistical

corrections based on DSE are moving

the census counts in the right direction,

though not far enough. Thus, the

statistical correction improves numeric

accuracy when the groups subject to

correlation bias are also undercounted

by the census. In fact, the group

identified by Demographic Analysis as

probably subject to significant

correlation bias in 1990 ‘‘ adult Black

males ‘‘ also had a high estimated

undercount rate from the 1990 PES.67

The Census Bureau expects that a

properly designed and conducted

coverage measurement survey should

improve both numeric and distributive

accuracy, even accepting that

correlation bias cannot be eliminated.

The Census Bureau will continue to use

Demographic Analysis to assess the

possibility of correlation bias at the

national level.

Accuracy at Different Geographic Levels

When Secretary Mosbacher decided

not to use the adjusted data in 1991, he

indicated that the adjusted data could

not be shown by convincing evidence to

be more distributively accurate at the

national, state, and local levels. The

June 1991 Undercount Steering

Committee report and later the August

1992 CAPE report concluded that

adjustment, on average, improved

distributive accuracy for states and areas

with populations of more than

100,000.68 The CAPE report, however,

left the erroneous impression that the

unadjusted census was more accurate at

small geographic areas, generally, areas

with a population of fewer than

100,000.

Analysis and Response

The CAPE report, issued on August 7,

1992, was followed by a November 25,

1992, Addendum. Because the CAPE

work was conducted at the request of

Secretary Mosbacher, the committee

implicitly adopted the framework of the

Mosbacher adjustment decision process

in reaching its conclusions. That is, the

adjusted census counts had to be shown

to be more accurate at state and local

levels in order to be adopted. The

committee determined that it was

unable to show that the adjusted census

counts were more distributively

accurate than the unadjusted counts for

areas with fewer than 100,000 in

population. Accordingly, the CAPE

concluded that the unadjusted counts

should be used in the postcensal

estimates program. Unfortunately, the

initial CAPE report could be interpreted

as indicating that there was a problem

with the accuracy of the adjusted census

numbers for areas with a population of

fewer than 100,000.

It is important to understand,

however, that the Census Bureau did

not stop its research into small area

accuracy with the initial CAPE report.

The initial CAPE analysis reported the

Census Bureau’s results from its first

comparisons, comparisons of similar

areas. For example, areas with

populations of fewer than 25,000 were

compared to each other, and major

metropolitan areas were compared to

each other. But the Census Bureau

conducted additional research,

comparing large cities and counties to

each other, to the balance of the nation,

and to the balance of their respective

states. This additional research reported

in the Addendum documented

additional evidence of improvements in

distributive accuracy at sub-state

levels.69

The correct interpretation of the CAPE

report and the Addendum is that the

Census Bureau could distinguish no

improvement in distributive sub-state

accuracy if the corrected numbers had

been used to produce estimates for areas

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38389

70Obenski and Fay, ‘‘Analysis of CAPE Findings

on PES Accuracy.’’

71Bell, ‘‘Using Information from Demographic

Analysis in Post-Enumeration Survey Estimation,’’

1106–1118; and Robinson and others, ‘‘Estimates of

Population Coverage in the 1990 United States

Census,’’ 1061–77.

72 Department of Commerce, ‘‘Adjustment of the

1990 Census,’’ 33587. 73Bureau of the Census, ‘‘Technical Assessment

of the Accuracy of Unadjusted Versus Adjusted

1990 Census Counts,’’ 4.

74Census Bureau Director Dr. Prewitt provided

examples of such operational difficulties in his

February 14, 2000, letter to Chairman Dan Miller of

the House Subcommittee on the Census. These

examples include: (1) Problems with the payroll

system that prevent the Census Bureau from paying

its employees on a timely basis; (2) widespread

problems filling enumerator positions, despite the

agency’s extensive pool of qualified applicants; and

(3) problems with the Census 2000 address file that

prevent Census Bureau employees from being able

to fulfill their responsibilities.

with populations of less than 100,000. It

is incorrect to infer that the unadjusted

census produced more distributively

accurate sub-state data. That question

was not tested in the CAPE research.

More recently, the Census Bureau has

re-examined the CAPE data and

determined that, based on available

data, there is no basis for concluding

that the unadjusted census was more

distributively accurate than the adjusted

counts for small areas.70 That is, in

general, no differences in the

distributive accuracy of these two sets of

counts have been demonstrated for

geographic areas with less than 100,000

population.

Based on the CAPE and subsequent

research and the expectation that the

error structures of the initial census and

A.C.E. operations for Census 2000 will

be similar to 1990, the Census Bureau

expects that the A.C.E. will, on average,

increase distributive accuracy for areas

with 100,000 or more residents. For

areas with fewer than 100,000 people,

the predicted effect of the A.C.E. on

distributive accuracy is indeterminate—

neither favoring the initial census nor

the corrected counts.

With respect to numeric accuracy, as

noted above, the Census Bureau expects

that the A.C.E. will, on average, improve

accuracy for geographic areas down to

and including census tracts.

Furthermore, the Census Bureau expects

that improvement will be greatest for

those areas that contain groups that

have been historically undercounted.

Consistency with Demographic Analysis

The analysis of the 1990 coverage

measurement survey included a

comparison of the adjusted census with

estimates based on Demographic

Analysis (DA).71 Discrepancies between

the adjusted census and DA estimates

led Secretary Mosbacher and others to

question the accuracy of the 1990

adjusted census counts.

Analysis and Response

Demographic Analysis uses records

and estimates of births, deaths,

immigration, Medicare enrollments and

estimates of emigration and

undocumented immigration to estimate

the national population, separately from

the census. These demographic

benchmarks are compared to the census

counts, and the differences are used to

create an estimate of the net census

undercount. These estimates are

produced for age groups (single years of

age), sex, and broad race groups (Black,

Non-Black). DA estimates can be used as

independent benchmarks to validate the

accuracy of coverage measurement

survey estimates for corresponding

demographic categories.

It is important to note that DA, like

coverage measurement surveys, has an

associated level of uncertainty. The

Census Bureau developed quantitative

measures of uncertainty for the 1990 DA

estimates, but these measures are based

in part on professional judgment about

the range of error in each of the

underlying demographic components.

How much uncertainty to assign to a

DA estimate is therefore a matter of

judgment. Different conclusions will be

reached depending on basic

assumptions about the accuracy of vital

statistics and other records used in DA.

In 1990, the Undercount Steering

Committee concluded that the

uncertainty in the DA estimates was of

a magnitude that meant that many of the

differences with the coverage

measurement survey estimates resulted

from random variation. However,

Secretary Mosbacher reached another

conclusion, citing several ‘‘important

and puzzling differences’’ between the

survey estimates and the DA

estimates.72 The Census Bureau, based

on previous work in this area,

concluded that some noted differences

were expected, but these differences did

not call into question the results of the

coverage measurement survey.73 Indeed,

the difference between the DA and 1990

PES estimates for adult Black males was

beyond the bounds of uncertainty,

demonstrating the utility of

Demographic Analysis for assessing

correlation bias at the national level.

Other differences fell within acceptable

bounds of uncertainty associated with

both sets of estimates. The Census

Bureau considered all differences

between the DA estimates and coverage

measurement survey estimates in its

determination that the coverage

measurement survey did improve the

accuracy of the census counts. For

Census 2000, the Census Bureau will

continue to compare both the

uncorrected and corrected census

counts with DA estimates.

Timing

In 1990, the adjusted data were not

available for release until July 1991.

This raises a concern about whether the

Census Bureau can produce the

statistically corrected data within the

statutory deadline of April 1, 2001, for

redistricting, without sacrificing the

quality of the initial census or the A.C.E.

Analysis and Response

The timing and quality of the initial

census and the A.C.E. are related. The

Census Bureau has developed a

schedule for the initial census and for

the A.C.E. operations that allows

adequate time to produce uncorrected

data for apportionment and corrected

data prior to the statutory deadline.

Barring some major, unanticipated

operational difficulty,74 the Census

Bureau expects to complete all data

collection and processing functions for

the initial census and the A.C.E. in time

to deliver quality, statistically corrected

redistricting numbers to the states prior

to April 1, 2001.

Critical differences between the 1990

census and plans for Census 2000

should allow production of the

corrected numbers within the required

period. First, the 1990 plan was not

premised on producing the adjusted

numbers by the April 1 deadline. In fact,

the 1990 litigation established a

deadline of July 15, 1991, for delivery of

the adjusted data.

Second, there are improvements to

the census that will make the initial

Census 2000 operations more timely.

While these improvements are directed

at allowing enumeration data collection

to occur closer to Census Day and

therefore to be more accurate, they will

also allow for an earlier start for the

A.C.E. With respect to the key issue of

staffing nonresponse followup so as to

finish on schedule, which is crucial to

the progress of both the census and the

A.C.E., the Census Bureau has

developed strategies to avoid the

recruitment and retention problems that

extended the 1990 census NRFU

operation. The Census Bureau has

conducted extensive research on how to

ensure the recruitment and retention of

well-qualified temporary employees.

These strategies, successfully employed

during the Census 2000 dress rehearsal,

included the targeting of wage rates to

local areas and a technique called

frontloading. Frontloading is directed at

38390 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

75Bureau of the Census, ‘‘Characteristics of

Census Errors,’’ by Deborah Griffin and Christopher

Moriarity, 1990 Decennial Census Preliminary

Research and Evaluation Memorandum No. 179, 15

September 1992; and General Accounting Office,

Decennial Census—1990 Results, 47.

76These coverage improvement programs are

discussed briefly in Cohen, White, and Rust,

Measuring a Changing Nation, 32–33.

77Bureau of the Census, ‘‘Adjustment of the 1990

Census,’’ passim. 78The NAS agrees that design changes in the

A.C.E. will reduce the variance in block sampling

weights, a ‘‘key improvement in comparison to the

1990 design,’’ May 3, 1999, letter from Janet L.

Norwood, Chair, NAS Panel to Review the 2000

Census, to Kenneth Prewitt, Director, U.S. Bureau

of the Census. 79Bureau of the Census, ‘‘Adjustment of the 1990

Census,’’ and Leo Breiman, ‘‘The 1991 Census

Adjustment: Undercount or Bad Data?’’ Statistical

Science 9, no. 4 (1994): 458–537. 80 David A. Freedman and Kenneth Wachter,

University of California, letter to Rep. Miller,

Chairman, House Subcommittee on the Census, 17

May 2000; and Brown and others, ‘‘Statistical

Controversies in Census 2000.’’

81Bureau of the Census, ‘‘Technical Assessment

of the Accuracy of 1990 Census Counts,’’4; and

Mary H. Mulry and Bruce D. Spencer, ‘‘Accuracy

of the 1990 Census and Undercount Adjustments,’’

Journal of the American Statistical Association 88

(September 1993): 1080.

82Bureau of the Census, ‘‘Technical Assessment

of the Accuracy of 1990 Census Counts,’’ 1.

reducing the effects of early turnover of

employees by hiring two employees for

every position. As a result of these and

other changes, nonresponse followup

will take place in a shorter time period

in Census 2000. This shortening of

nonresponse followup is in accord with

the observations of the Census Bureau

and the General Accounting Office that

NRFU results decrease in accuracy as

the time from Census Day increases.75 In

addition, Census 2000 will not be

repeating certain ineffective coverage

improvement programs that delayed

processing of the initial census in the

1990 coverage measurement survey.76

Third, several important changes will

improve the timeliness of the A.C.E.

operation. For example, the A.C.E.

interviewers will have received more

extensive training than in 1990.

Additionally, the Census Bureau has

developed a Computer Assisted Person

Interviewing (CAPI) system for the

A.C.E. that will allow enumerators to

collect the data more quickly and

accurately, and to transmit it

electronically in a more expeditious

manner by using laptop computers.

In the unlikely event of an

unanticipated, major operational

difficulty, the Census Bureau will not

curtail important operations key to the

quality of the entire census to stay on

schedule. For example, the Census

Bureau will not curtail nonresponse

followup in difficult-to-enumerate

neighborhoods to stay on the A.C.E.

schedule. Likewise, the Census Bureau

will not curtail the A.C.E. data

collection activities. The Bureau is

committed to achieving high quality in

all census operations, and Census

Bureau statisticians will be monitoring

key A.C.E. performance information,

such as response rates, for early warning

about areas warranting corrective

actions.

Level of Sampling Variance/Smoothing

The levels of sampling variance and

bias in the 1990 coverage measurement

survey were important topics in the

adjustment debate. Sampling variance is

discussed in this section; bias will be

discussed in the following section.

Analysis and Response

One issue in 1990 was the use of a

statistical technique called smoothing, a

complex, model-based method designed

to control sampling variance. The use of

smoothing led to an extensive

discussion regarding the robustness of

the 1990 methodology. For Census 2000,

the Census Bureau has developed the

A.C.E. sample design so that smoothing

will not be necessary. There were also

concerns about the overall level of

sampling variance in the 1990 coverage

measurement survey.77 In developing

the A.C.E. design, the Census Bureau

thoroughly examined 1990 variance

issues and made important design

decisions to reduce sampling variance

levels. These include:

• The A.C.E. sample size is almost

double that of 1990, increased from

approximately 165,000 to 314,000

housing units. Because sampling

variance is inversely proportional to

sample size, this increase will reduce

the level of sampling variance in 2000.

• The A.C.E. sample was designed to

minimize the range in size of the

sampling weights. Weights are assigned

to categories of blocks (that is, small and

large) that have different probabilities of

being selected in the sample. When

there is a wide range of weights,

variance increases because blocks with

large weights have a disproportionate

effect on the variance of the estimates.

The Census Bureau has designed its

sampling procedures for Census 2000

specifically to limit how much these

weights will vary. This design will

result in reduced sampling variance.78

The Census Bureau has used the 1990

experience to develop an enhanced

A.C.E. sampling design, and does not

anticipate that variance-related issues

will be a serious source of concern for

the Census 2000 coverage measurement

survey.

Level of Nonsampling Error/Bias

One concern was that the level of

nonsampling error or bias in the 1990

coverage measurement survey was so

large that statistical correction would

not result in an improvement in

distributive accuracy.79 Critics of the

A.C.E. have expressed similar concern

about the anticipated level of bias in the

Census 2000 DSE.80

Analysis and Response

The Census Bureau conducted

extensive evaluations of nonsampling

error in the 1990 coverage measurement

survey.81 These evaluations have given

the Census Bureau a detailed

understanding of nonsampling error.

Based on this extensive work, the

Census Bureau has concluded that the

levels of nonsampling error in the 1990

PES did not prevent the statistical

correction based on the coverage

measurement survey from improving

the accuracy of the census counts.82 The

A.C.E. design includes enhancements to

the 1990 coverage measurement survey

that will even further control

nonsampling error.

It is important to note that some

amount of bias in both the initial census

and the A.C.E. is inevitable. However,

the Census Bureau’s analysis of bias,

grounded in sound statistical principles,

leads to the expectation that the

improvements described in the

following sections will control the

levels of nonsampling error in the

A.C.E. so that a statistical correction

based on the A.C.E. will improve the

uncorrected counts.

Enhancements to the Matching Process

Matching refers to the determination

of whether an individual enumerated in

a coverage measurement survey is the

same person as an individual

enumerated in the initial census

operation. Because errors in matching

can significantly affect undercount

estimates, highly accurate matching is

an important component of the A.C.E.

methodology. Although neither

Secretary Mosbacher nor CAPE

identified matching error as a significant

problem with the 1990 coverage

measurement survey, the Census Bureau

has made significant improvements to

the matching process in the 2000 A.C.E.

design, and matching error is expected

to be even lower in Census 2000 than

in 1990:

• A fully automated system supports

computer and clerical matching, an

advance over 1990 procedures that

required handling and control of paper

documents. This improvement provides

for a number of built-in edits and

quality checks to control matching error.

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38391

83Congress, House, Committee on Government

Reform and Oversight, Prepared Testimony of K.W.

Wachter and D.A. Freeman Before the House

Committee on Government Reform and Oversight,

104th Cong., 1st sess., 29 February 1996.

84Bureau of the Census, ‘‘Non-Response in

Census Coverage Measurement Surveys and Its

Impact—An Historical Review,’’ by Ruth Ann

Killion, DSSD Briefs, Information, and Topics

Memorandum Series No. 44C, 17 September 1998,

pp. 6–7.

85This intensive field operation designed to

minimize missing data is described in Childers and

Fenstermaker, ‘‘Accuracy and Coverage Evaluation:

Overview of Design,’’ 7.

86Secretary Mosbacher stated that levels of

missing data were sufficiently low so that variation

in the Census Bureau’s missing data models made

no difference in the outcome of the survey, and he

concurred with the Undercount Steering

Committee’s judgment that the outcome was robust

(Bureau of the Census, ‘‘Adjustment of the 1990

Census,’’ 33600). The CAPE, accordingly, did not

examine this issue.

87Brown and others, ‘‘Statistical Controversies in

Census 2000.’’

88T.R. Belin and others, ‘‘Hierarchical LogisticRegression Models for Imputation of Unresolved

Enumeration Status in Undercount Estimation,’’

Journal of the American Statistical Association 88

(September 1993): 1149–66; and Bureau of the

Census, ‘‘Documentation of Handling Unresolved

Enumeration Status in 1990 Census/PostEnumeration Survey,’’ by Greg Diffendal and Tom

Belin, STSD Decennial Census Memorandum Series

V–98, 15 January 1991.

The automated matching system is the

culmination of Census Bureau analyses

and refinements over the last 20 years

and will make searching and matching

easier and more reliable.

• The matching processes have been

centralized in one site, rather than

decentralized as in 1990, allowing for

more effective control—a well-trained

staff will perform all matching at a

single location.

• As discussed below, the change in

the treatment of people who have

moved since Census Day will simplify

matching for these movers. Unlike in

1990, it will only be necessary to match

people who resided in the sample

blocks on April 1.

Enhancements to Computer Processing

After the initial release of the adjusted

numbers in July 1991, the Census

Bureau discovered a computer

processing error that resulted in a 0.4

percent decrease in the estimated

undercount for the 1990 census. The

CAPE report reduced the Census

Bureau’s official undercount estimate

from 2.1 percent to 1.6 percent, with 0.4

percentage points attributable to the

computer processing error, and 0.1

percent attributable to additional

processing corrections. Concerns have

been raised relating to the Census

Bureau’s late discovery of the computer

processing error. These concerns have

been cited as evidence that the

complexity of the computer operations

associated with incorporating the results

of a coverage measurement survey—like

the A.C.E.—in the census counts makes

the final numbers vulnerable to

significant processing errors.83

The Census Bureau has adopted a

number of methods to improve the

quality of the A.C.E. software to guard

against a similar error in Census 2000:

• To ensure reliability, the Census

Bureau has included software validation

and verification strategies, such as

independent software development of

key computer programs (double

programming).

• To reduce ambiguity and increase

communication, the Census Bureau has

enforced standardized nomenclature

and adopted an improved

documentation approach for technical

issues.

• The Census Bureau has developed a

Sample Design Control System. This

system provided the necessary data to

control, monitor, and validate the

different phases of sampling. It also

ensured that the software used to select

the A.C.E. sample functioned correctly.

• The software programs supporting

the A.C.E. estimation process will be

further validated by an Integrated

Review System. This system will

provide data on all phases of the

estimation process that will allow

timely validation that the software is

performing as specified.

These and other initiatives should

result in a controlled, robust, and

reliable A.C.E. computer processing

environment. Therefore, the Census

Bureau expects the processing for the

Census 2000 A.C.E. to be not only more

streamlined but also more reliable than

it was for the 1990 PES.

Enhancements to Minimize Missing

Data

Missing data cases involve the

following situations where complete

information cannot be obtained: missing

characteristic data (race, age, or other

characteristic information), complete

non-interviews, or cases with

insufficient information to determine an

individual’s enumeration or match

status. In 1980, missing data in the

coverage measurement survey was a

serious problem and factored into senior

statisticians’ conclusion that the

estimates were not sufficiently reliable

to use for statistical adjustment of the

census counts. The Census Bureau took

steps to minimize missing data in the

1990 coverage measurement survey, and

missing data in 1990 did not

significantly affect the accuracy of the

estimates.84 Nonetheless, concerns

remain regarding the potential for high

levels of missing data in the A.C.E.

Building on its experience from the

1990 census, the Census Bureau has

designed its field operations to

minimize missing data. After the initial

A.C.E. interview attempt, the Census

Bureau will allow up to two additional

weeks for attempts to revisit any

nonresponding households. This twoweek period of intense followup of

nonresponding households will be

conducted by the Census Bureau’s best

and most experienced available A.C.E.

interviewers.85 Finally, Census Bureau

staff will be monitoring missing data

rates closely throughout the conduct of

the A.C.E.

The Census Bureau has developed

additional extensive procedures to deal

with missing data. One method the

Census Bureau uses to handle missing

data in both the initial census and the

A.C.E. is imputation. Imputation is an

established statistical methodology that

completes missing respondent

information by incorporating

information provided by other similar

respondents. The imputation process for

Census 2000 draws on lessons learned

in the 1990 census. Additionally, the

imputation process for Census 2000 has

been simplified, which should result in

the production of more easily validated

data.

While missing data were not a

significant issue for the 1990 census,86

some concerns have been expressed

regarding the accuracy and robustness

of the Census Bureau’s imputation

model for the 1990 coverage measure

survey.87 However, Census Bureau

statisticians and others have conducted

multiple evaluations using different

methodologies to independently

validate the imputation model used in

the 1990 census.88 These evaluations

and the improvements to missing data

procedures discussed earlier lead the

Census Bureau to expect that missing

data will not be a substantial problem in

the A.C.E.

Homogeneity and the Synthetic

Assumption

Generally speaking, homogeneity

refers to the principle that individuals

grouped in a post-stratum have similar

probabilities of being included in the

census, that is, similar coverage

probabilities. If homogeneity holds,

conclusions can be drawn from a

sample about population groups or

geographic areas and the initial

enumeration for these population

groups or areas can be corrected with a

coverage measurement survey. The

synthetic assumption states that the

people in a particular post-stratum are

38392 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

89 K. Wachter and D. Freedman, ‘‘Local

Heterogeneity and Census Adjustment for the

Intercensal Base,’’ Technical Report No. 381

(Berkeley, CA: University of California, Department

of Statistics, 1993); and Brown and others,

‘‘Statistical Controversies in Census 2000,’’ 13.

90This section presents a general discussion of

the basis for synthetic or indirect estimation. There

are more complex, but less stringent, requirements

involving the relationship between census

omissions and erroneous enumerations as discussed

in Howard Hogan’s paper, ‘‘Accuracy and Coverage

Evaluation: Theory and Application.’’

91 David Freedman and Kenneth Wachter,

‘‘Planning for the Census in the Year 2000,’’

Evaluation Review, 20, (August 1996): 355–77.

92Bureau of the Census, ‘‘Accuracy and Coverage

Evaluation Survey: Final Post-stratification Plan for

Dual System Estimation,’’ by Richard Griffin and

Dawn Haines, DSSD Census 2000 Procedures and

Operations Memorandum Series Chapter Q–24, 19

April 2000.

93 Ibid.

94Robert E. Fay and John Thompson, ‘‘The 1990

Post Enumeration Survey: Statistical Lessons in

Hindsight,’’ in Proceedings of the 1993 Annual

Research Conference, 21–24 March 1993.

95 Griffin and Haines, ‘‘Accuracy and Coverage

Evaluation Survey: Final Post-stratification Plan for

Dual System Estimation.’’

relatively homogeneous and will

generally share the same coverage

factor. There are concerns, however,

that a lack of homogeneity could lead to

inaccuracies being introduced into the

data for areas or population groups

within the post-stratum.89

Analysis and Response

At issue is not whether there is

perfect homogeneity; at issue is whether

heterogeneity is too great to prevent an

improvement from using the A.C.E.

While the degree to which the

homogeneity assumption holds is a

continuing issue, the Census Bureau has

made design improvements to the

A.C.E. to control heterogeneity and

believes that heterogeneity will not

preclude the production of useful small

area data in Census 2000.

The statistical correction that results

from the A.C.E. is carried down to

census blocks by applying the coverage

correction factors within each A.C.E.

post-stratum. The goal in constructing

post-strata is to form groupings of the

population that capture differences in

the probabilities of being included in

the census and the A.C.E.90 In effect, the

inclusion probabilities are more similar

for individuals within the same poststratum than for individuals in different

post-strata. The coverage correction

factors are calculated for each poststratum, based on a representative

sample of the post-stratum, and thus

reflect the net coverage of all people

within the post-stratum. This is the

underlying basis for applying this factor

to the data records within the

corresponding post-stratum to produce

statistically corrected block totals which

serve as the basis for Census 2000

tabulations.

The more homogeneity within a poststrata and the more differences among

post-strata, the greater the improvement

from statistical correction. In designing

post-strata, it is not necessary for each

individual to have the same probability

of inclusion. Since no two individuals

are perfectly alike with respect to their

chances of being included in either the

initial census or the A.C.E., the goal for

defining post-strata is to form groupings

of the population with similar inclusion

probabilities. That is, the goal is to form

post-strata that differentiate between

groups of the population with respect to

inclusion probabilities, and with respect

to net coverage in the initial census.

Some have suggested that an

improvement will result from applying

Demographic Analysis-based

corrections within national post-strata

consistent with DA.91 However, the

Census Bureau expects to achieve

greater improvements by having defined

post-strata that take advantage of more

local data.92

The accuracy of the estimates that

result from the application of the

coverage correction factors depends on

the degree to which the net coverage for

areas or groups within a post-stratum is

similar to the coverage correction factor

that was developed for that poststratum. The coverage correction factor

is measured for the post-stratum based

on a representative sample, and thus

represents the net coverage for the poststratum. Clearly, within the poststratum, some degree of variation is

expected from the measured coverage

correction factor, and this variation will

most likely be relatively greater for

small areas. Thus, it is inevitable that

the A.C.E. will result in the population

in some blocks being overestimated and

the population in other blocks being

underestimated. The A.C.E. statistical

correction was never intended nor

expected to produce unqualified

improvement in the smallest geographic

areas, like blocks. That the A.C.E. does

not produce improvement for every

single block, however, is no reason to

forego the benefits that will flow from

the use of corrected census population

counts at geographic levels of

significance to data users. The Census

Bureau expects that the A.C.E. estimates

will produce better data for

aggregations—such as states,

congressional districts, counties, and

cities—that are the basic areas for which

census data are used.

The Census 2000 A.C.E. incorporates

improvements from the design used for

the 1990 coverage measurement survey

that are expected to improve the

homogeneity within post-strata for

Census 2000.93 The Census Bureau

analyzed heterogeneity as part of the

1990 CAPE process, and has continued

research for the A.C.E. post-strata.94

Building on the lessons learned from

1990, the Census Bureau has developed

enhanced post-strata for Census 2000.

For example, the A.C.E. post-strata

definitions include mail return rate and

type of enumeration variables.95

Some have cited the CAPE report as

evidence that the Census Bureau had

serious concerns about heterogeneity. A

reading of the entire CAPE report,

including the more technical

Addendum, puts these concerns in

proper perspective. That is, the full

analysis of the CAPE report (including

the Addendum) supports the

expectation of the Census Bureau that

the use of the A.C.E. results will lead to

improvements in the accuracy of the

Census 2000 data.

Additional Design Changes From 1990

In addition to the specific

improvements discussed previously, the

Census Bureau has implemented other

changes to the 1990 coverage

measurement survey design. These

changes, which will improve

operational efficiency, include the use

of the telephone in the A.C.E., and

changes in the treatment of movers and

the search area for matching. The

Census Bureau will also collect data on

race and ethnicity differently in Census

2000. The Census Bureau continues to

consider and examine issues relating to

these changes.

Use of the Telephone in A.C.E.

Interviewing

To gain efficiencies in the

interviewing phase of the A.C.E.,

enumerators will conduct telephone

interviews using CAPI laptop computers

for households that have returned their

census questionnaires by mail. By

design, this interview will take place

before or concurrent with the initial

census nonresponse followup. The

interviews will be conducted from the

homes of the A.C.E. enumerators and

will be conducted only for households

that mail back a questionnaire that

includes a telephone number.

Furthermore, the households must be in

areas where there is negligible risk of

mail delivery problems—generally,

single family housing units or large

multi-unit structures in areas with citystyle mail delivery.

The Census Bureau implemented this

process to enhance the efficiency and

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38393

96Hogan, ‘‘Accuracy and Coverage Evaluation

Theory and Application,’’ 22.

97Bureau of the Census, ‘‘Minutes of the

Executive Steering Committee on Accuracy and

Coverage Evaluation Policy (ESCAP),’’ 5 January

2000.

98Hogan, ‘‘1990 Post-Enumeration Survey,’’ 1054.

99Childers and Fenstermaker, ‘‘Accuracy and

Coverage Evaluation: Overview,’’ 8–9; and Bureau

of the Census, ‘‘Accuracy and Coverage Evaluation:

The Design Document,’’ by Danny R. Childers,

DSSD Census 2000 Procedures and Operations

Memorandum Series Chapter S–DT–01.

100Bureau of the Census, ‘‘Accuracy and

Coverage Evaluation Survey: Targeted Extended

Search Plans,’’ by Alfredo Navarro, DSSD Census

2000 Procedures and Operations Memorandum

Series #Q–18, 12 January 2000.

101President, Executive Office, Office of

Management and Budget, ‘‘Revisions to the

Standards for the Classification of Federal Data on

Race and Ethnicity,’’ Federal Register, (30 October

1997), vol. 62, no. 210, pp. 58782–90.

102The Census Bureau’s plan for including

individuals in the A.C.E. post-strata who report

more than one race is described in Griffin and

Haines, ‘‘Accuracy and Coverage Evaluation

Survey: Final Post-stratification Plan for Dual

System Estimation,’’ 1–2.

quality of the A.C.E. interview.

Shortening the elapsed time from

Census Day to the A.C.E. enumeration

should improve data quality. Also,

starting early in an environment that is

more easily controlled should allow the

A.C.E. enumerators to gain valuable

experience in conducting interviews

and in operating their laptop computers.

The Census Bureau designed this

process in a fashion that should

maintain the independence between the

A.C.E. and the other Census 2000

operations.

New Treatment to Account for Movers

The Census Bureau has changed its

treatment of individuals whose

residence changes after Census Day. In

the 1990 coverage measurement survey,

movers were sampled where they lived

at the time of the PES interview. The

Census Bureau then searched the census

records at the movers’ April 1 usual

residence to determine if they had been

correctly enumerated in the census.96

In the modified procedure employed

by the A.C.E., the Census Bureau will

combine information on movers from

two sources to produce an estimate of

movers who are missed in Census 2000.

First, an estimate of the total number of

movers will be calculated based on

people who moved into the A.C.E.

sample blocks between April 1 and the

time of the A.C.E. interview. Second,

the rate at which movers match to

Census 2000 will be based on

reconstructing the Census Day residents

of the A.C.E. sample housing units and

matching these residents to the initial

census records. Reconstructing the

Census Day residents will be based on

proxy interviews with the new residents

or neighbors. These two estimates will

be combined to form an estimate of the

movers who are missed in Census 2000.

These results are then used in the Dual

System Estimation. The Census Bureau

tested the modified procedure in the

dress rehearsal and has judged this

procedure to be the best blend of

operational feasibility and accuracy.97

Search Area for Matching

The Census Bureau’s search operation

in the 1990 coverage measurement

survey used an extended search area in

blocks adjacent to the sample blocks.98

The extended search area included one

ring of adjacent blocks, or two rings of

adjacent blocks in most rural areas. A

person located in either the sample or

an adjacent block was labeled a correct

enumeration or match. Defining the

search area in this fashion provided

significant gains in reducing sampling

variance. For Census 2000, the A.C.E.

search area has been designed to

achieve the gains in controlling

sampling variance, while providing

operational efficiencies.

The Census 2000 search operation

uses a sampling procedure that selects

A.C.E. block clusters for an extended

search. All block clusters are selected

where there is evidence that an

extended search will provide substantial

information needed for the A.C.E.

matching. Additionally, a random

subsample of all other clusters is

selected for the extended search.99 This

decision was based on an analysis of the

results of the 1990 census coverage

measurement survey matching that

indicated that this strategy would

provide virtually the same gains in

sampling variance reduction as

compared to the 1990 results.100

Reporting More Than One Race

In accordance with direction from the

Office of Management and Budget,101

Census 2000 will for the first time allow

individuals to report more than one

racial category. This guidance from the

OMB necessitates that the A.C.E. poststrata be defined taking into account

people that report more than one race.

The Census Bureau, therefore, has

defined and documented the A.C.E.

post-strata to include individuals that

report more than one race.102 The

Census Bureau will conduct a study of

the effects of multiple race reporting

after completion of the census.

Making the Final Decision

The Census Bureau expects that the

A.C.E., if properly conducted, will make

the census more accurate by improving

coverage and reducing differential

undercounts. The Census Bureau will

not, however, release corrected

redistricting data until it has brought its

technical judgment to bear in assessing

the available data to verify that its

expectations have been met. The Census

Bureau will consider operational data to

validate the successful conduct of the

A.C.E., assess whether the A.C.E.

measurements of undercount are

consistent with historical patterns of

undercount and independent

Demographic Analysis benchmarks, and

review measures of quality.

In preparing for this determination,

the criteria and the process that will be

followed for the assessment of the

A.C.E. results will be shared and

discussed with outside statistical

experts and other interested parties in

the fall of 2000. This plan is consistent

with the principle of pre-specification

adopted by the Census Bureau for the

Census 2000 A.C.E. and with its open

and transparent planning and decision

processes. The extent of prespecification already publicly provided

is very extensive.

It should be noted that all major

census operations are vulnerable to

unanticipated difficulties. Such

difficulties could affect production of

the apportionment counts. If, for

example, a major natural disaster were

to occur in a region of the country

during census nonresponse followup,

and this operation were seriously

disrupted, the Census Bureau might

conclude that the apportionment count

so misrepresented the ‘‘true’’ state-bystate population distribution that it

should not be used until corrective

action was taken, possibly delaying

delivery of the apportionment counts

past January 1, 2001. Unanticipated

difficulties could also affect the A.C.E.

The Census Bureau would respond to

any major unanticipated operational

difficulty by taking steps to conduct and

complete (or repeat, as necessary) all

planned operations necessary to ensure

that an accurate A.C.E. had taken place

before releasing the statistically

corrected data. If the Census Bureau

determines that incorporating the

results of the survey would not improve

the accuracy of the initial census

counts, then the uncorrected data would

be denominated as the P.L. 94–171 file.

Secretary Mosbacher’s 1991 decision

document raised the specter of

‘‘political tampering’’ in any use of

statistically corrected census data. To

avoid even the appearance of political

manipulation, the Census Bureau has

proposed a process for verifying the

agency’s expectations regarding the

improvements in accuracy from the

A.C.E. Under that proposal, a committee

38394 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

of senior Census Bureau officials

responsible for resolving policy and

technical issues regarding the A.C.E.

and assessing the technical effectiveness

of its operations would make a

recommendation to the Census Bureau

Director regarding the use of the

statistically corrected census data. The

Director would make a determination

regarding the use of the statistically

corrected data, taking into consideration

the recommendation of the committee.

This committee, known as the Executive

Steering Committee for A.C.E. Policy

(ESCAP), was formed in late 1999 and

normally meets every two weeks to

discuss technical and policy issues

associated with the A.C.E. and to advise

the Director on these issues. The ESCAP

is chaired by the Associate Director for

Decennial Census and includes the

following other senior career staff:

Deputy Director; Principal Associate

Director and Chief Financial Officer;

Principal Associate Director for

Programs; Associate Director for

Methodology and Standards; Associate

Director for Demographic Programs;

Assistant Director for Decennial Census;

Chief, Decennial Statistical Studies

Division; Chief, Planning, Research and

Evaluation Division; Chief, Population

Division; Chief, Decennial Management

Division; and Senior Mathematical

Statistician. The committee will

document its discussions and decisions

and will make this documentation

available along with its

recommendation to the Director.

Following the release of census data,

the Census Bureau will continue its

research and evaluation, budget

permitting. The census is an ongoing

process, and the Census Bureau

implements refinements to the data over

a 10-year period. These ongoing efforts

are consistent with good science and are

fundamental to the Census Bureau’s

work. The fact that further research will

provide more information about the

success of census operations, including

the production of the apportionment

counts and the A.C.E., does not alter the

requirement to release the statistically

corrected block-level numbers by the

April 1, 2001, statutory deadline, if

these data meet the Census Bureau’s

expectations with regard to

improvements in accuracy. Evaluations

of many Census 2000 operations and

results, including the A.C.E., will

continue after the release of the data;

and program evaluation results will be

available for planning the 2010 census

and informing the scientific and public

discourse over the intervening years.

Conclusions

The Census Bureau’s mission is to

produce the most accurate data possible,

taking into account the intended uses of

the data. The extensive body of research

that the Census Bureau has conducted

on census undercount, including the

1990 census evaluations, has

conclusively demonstrated that

traditional census methodologies will

not effectively reduce the differential

undercount. The Census Bureau has

concluded that based on current stateof-the-art science, the best method or

procedure that has the potential to

reduce the differential undercount and

thereby increase accuracy is the

application of scientific sampling to

improve traditional census methods.

This view is widespread, though not

unanimous, in the professional

statistical community.

At the present time, the Census

Bureau has also concluded that it is

operationally feasible to complete the

A.C.E. and produce statistically

corrected census data prior to April 1,

2001, and expects that the corrected

data will be the most accurate data

available. The Census Bureau’s final

decision on what data to release as the

most accurate data will not be made,

however, until the Census Bureau has

had an opportunity to review the

conduct of the census and the A.C.E.

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Statistics, 1993.

White, Andrew A., and Keith F. Rust, eds.

Sampling in the 2000 Census: Interim

Report I. Washington, D.C.: National

Academy Press, 1996.

ll. Preparing for the 2000 Census: Interim

Report II. Washington, D.C.: National

Academy Press, 1997.

Wolter, Kirk M. ‘‘Some Coverage Error

Models for Census Data.’’ Journal of the

American Statistical Association 81

(June 1986): 338–46.

Wright, Tommy and Joyce Farmer. ‘‘A

Bibliography of Selected Statistical

Methods and Development Related to

Census 2000.’’ 3rd ed., 1 May 2000.

June 13, 2000.

MEMORANDUM FOR KENNETH PREWITT

From: William M. Daley

Attached is my decision adopting the

analysis and conclusions set forth in

‘‘Accuracy and Coverage Evaluation:

Statement on the Feasibility of Using

Statistical Methods to Improve the Accuracy

of Census 2000.’’

The Department of Commerce and the

Census Bureau are committed to making

certain that the decennial census, the largest

peacetime mobilization in our country’s

history, produces the most accurate count

possible of the individuals in our Nation. The

census is an important civic undertaking

designed to find out who we are and how we

live. We owe it to the American people to use

all of the tools at our disposal to make the

census as accurate as possible.

For decades, the experts at the Census

Bureau and within the statistical community

have recognized that the methodology used

in the past fails to count many Americans.

This phenomenon ‘‘ called the undercount ‘‘

has been measured since the 1940s. More

disturbing, however, is the established fact

that the undercount operates differently for

different population groups, creating an

inequity called the differential undercount.

Despite the Census Bureau’s best efforts, the

differential undercount has persisted and, for

at least the last 50 years, has meant that some

groups in the population are undercounted

and therefore underrepresented in political,

resource-allocation, and other decisions.

The choice we face is whether to use

modern statistical methods to produce a

more accurate census, or whether we do

nothing. Under the law, statistical methods

may not be used in tabulating the population

for purposes of apportioning seats in the

House of Representatives, but I am required

to authorize the use of modern statistical

methods, if ‘‘feasible,’’ for all other releases

of census data.

38396 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

1Constitution, Art. I, Sec. 2, Cl. 3.

2Wisconsin v. City of New York, 517 U.S. 1

(1996).

The Director of the Census, with guidance

from the Department concerning the relevant

legal standard, has provided an analysis of

the feasibility of using statistical sampling to

correct the persistent errors in the census and

to improve its accuracy—‘‘Accuracy and

Coverage Evaluation: Statement on the

Feasibility of Using Statistical Methods to

Improve the Accuracy of Census 2000.’’ As

explained in that document, absent the use

of statistical methods there is no way to

correct the persistent differential undercount

in Census 2000. With established statistical

methods, however, the Census Bureau

believes that it will be able to correct these

errors and improve the overall accuracy of

the census by increasing coverage and

reducing the differential undercount.

I hereby adopt the analysis and

conclusions of the Director of the Census set

forth in ‘‘Accuracy and Coverage Evaluation:

Statement on the Feasibility of Using

Statistical Methods to Improve the Accuracy

of Census 2000.’’ As explained in that

document, the expert staff at the Bureau

believe that the Accuracy and Coverage

Evaluation Survey, which was designed to

measure and correct for the overall

undercount and the differential undercount,

should make the census counts more

accurate. As is appropriate, however, no final

decision about whether to correct the census

counts can be made until the operations have

been completed and considered by the

Bureau. The Director will make a final

decision before April 1, 2001, the deadline by

which the Bureau must provide data to the

States for redistricting.

I am also proposing today a regulation that

will insulate the final decision on whether to

correct the census counts from even the

appearance of political tampering and will

make the decision-making process as

transparent as possible. Because the final

decision on whether to correct the census is

a technical decision, the proposed regulation

would delegate my authority over that

decision to the Director of the Census. His

decision would, in turn, be informed by a

public recommendation made by a group of

career experts at the Census Bureau. Through

this process, we will be able to ensure public

confidence in the final decision.

Dated: June 13, 2000.

William M. Daley,

Secretary of Commerce.

June 12, 2000.

MEMORANDUM TO: The Secretary, The

Director of the Census

FROM: Andrew J. Pincus

SUBJECT: Legal Obligation to Produce

Statistically-Corrected NonApportionment Census Numbers

As you know, the Department of

Commerce and the Census Bureau have been

reviewing what process to use in determining

whether to statistically correct census data

for purposes other than apportionment of the

House of Representatives. As part of this

review, we have examined the legal

requirements of the Census Act. After careful

analysis, we have concluded that Section 195

of the Census Act requires the Census

Bureau, if feasible, to produce statisticallycorrected numbers from the decennial census

for all non-apportionment purposes.

The feasibility determination is a technical

decision that should be made by the Director,

to whom the Secretary delegated his Title 13

responsibilities in Departmental

Organizational Order 35–2A (July 22, 1987).

To this end, we also believe it appropriate to

propose a regulation that would make certain

that the Director has final authority over the

feasibility determination.

I. Background

The Constitution requires Congress to

apportion seats in the House of

Representatives among the States every ten

years based on the results of the decennial

census, providing that ‘‘[t]he actual

Enumeration shall be made within three

Years after the first Meeting of the Congress

of the United States, and within every

subsequent Term of ten Years, in such

Manner as they [Congress] shall by Law

direct.’’ 1 Through the Census Act, which is

codified in title 13 of the United States Code,

Congress has delegated its broad authority

over the census to the Secretary of

Commerce.2 In particular, 13 U.S.C. 141(a)

provides that the Secretary of Commerce

shall take ‘‘a decennial census of [the]

population * * * in such form and content

as he may determine, including the use of

sampling procedures and special surveys.’’

As the Supreme Court recognized in

Wisconsin v. City of New York, the

Secretary’s determination as to how to

conduct the Census, pursuant to the

delegation of authority provided to him by

Congress, need only be reasonable, so long as

it is also ‘‘consistent with the constitutional

language and the constitutional goal of equal

representation.’’ Id. at 19. The Court further

recognized, in the context of the Secretary’s

decision in 1990 not to adjust the census,

that the ‘‘Constitution itself provides no real

instruction’’ on what methods the Secretary

should use in performing the Census. Id. at

18.

II. Section 195 of the Census Act Requires

the Census Bureau To Use Sampling When

‘‘Feasible’’ For Calculating the Population

For Purposes Other Than Apportionment of

Seats in the House of Representatives Among

the States

Section 195 of the Census Act states:

Except for the determination of population

for purposes of apportionment of

Representatives in Congress among the

several States, the Secretary shall, if he

considers it feasible, authorize the use of the

statistical method known as ‘‘sampling’’ in

carrying out the provisions of this title.

13 U.S.C. 195. Section 195 refers

specifically to only one of the many

uses of census data. Decennial census

data are used not only by the U.S.

Congress for apportioning seats in the

House of Representatives among the

States, but also by the States in drawing

the lines for congressional and state and

local legislative districts, and by federal

and state agencies in allocating funds.

In Department of Commerce v. House

of Representatives, 119 S. Ct. 765

(1999), the Supreme Court held that

Section 195 does not permit the use of

sampling to produce population counts

for the purpose of apportioning seats in

the House of Representatives among the

States. Id. at 777 (‘‘there is only one

plausible reading of the amended § 195:

It prohibits the use of sampling in

calculating the population for purposes

of apportionment.’’). Here, the question

is what standard Section 195 applies

with respect to the calculation of

population by the Census Bureau for

purposes other than ‘‘apportionment of

Representatives in Congress among the

several States.’’ The plain language of

the provision supplies the answer:

Section 195 states that the Secretary

‘‘shall’’ authorize the use of statistical

sampling for all other purposes ‘‘if he

considers it feasible.’’ Thus, when

calculating population or other

information for a purpose other than

apportionment, the Secretary (or his

designee, the Census Bureau) must first

determine whether it is ‘‘feasible’’ to use

sampling, and—if the use of sampling is

feasible—its use must be authorized.

This interpretation of Section 195’s

plain language is confirmed by

Congress’s amendment of the provision

in 1976. Prior to that amendment,

Section 195 stated:

Except for the determination of population

for apportionment purposes, the Secretary

may, where he deems it appropriate,

authorize the use of the statistical method

known as ‘sampling’ in carrying out the

provisions of this title.

The pre-1976 wording (‘‘may, where he

deems it appropriate’’) gave the

Secretary the option of using sampling.

The 1976 amendment eliminated the

Secretary’s discretion, transforming

Section 195 into a mandatory directive

—the Secretary ‘‘shall * * * authorize

the use of’’ sampling for all other

purposes ‘‘if he considers it feasible.’’

The Census Act therefore

unambiguously requires, with respect to

non-apportionment calculations, that

when sampling is feasible, it must be

used.

The Supreme Court’s recent decision

in Department of Commerce v. House of

Representatives confirms this

conclusion. In explaining the purpose of

the 1976 amendments, the Court stated,

‘‘[t]hey changed a provision that

permitted the use of sampling for

purposes other than apportionment into

one that required that sampling be used

for such purposes if ‘feasible.’ 119 S.Ct.

at 778. The Court explained that

Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices 38397

3Some commentators have argued that the

Supreme Court reached a different conclusion in

Department of Commerce because it found standing

‘‘on the basis of the expected effects of the use of

sampling in the 2000 census on intrastate

redistricting’’ (119 S. Ct. at 774). The Court’s

standing decision, however, simply reflects a

conclusion that an individual claiming injury by

the use of that data for redistricting had alleged

sufficient Article III injury in fact to challenge the

plan. But the Census plan before the Court provided

for the collection and production of a single set of

sampling-adjusted data for use in both the

apportionment tabulation and the redistricting

tabulation. Because the Court invalidated the plan,

there was no need for the Court to apply Section

195 to the use of sampling for redistricting purposes

in order to redress these plaintiffs’ purported injury.

This conclusion is confirmed by the Court’s careful

limitation of its holding: ‘‘The District Court below

* * * concluded that the proposed use of

statistical sampling to determine population for

purposes of apportioning congressional seats among

the States violates the Act. We agree.’’ 119 S. Ct.

at 765.

‘‘section [195] now requires the

Secretary to use statistical sampling in

assembling the myriad demographic

data that are collected in connection

with the decennial census. But the

section maintains its prohibition on the

use of statistical sampling in calculating

population for purposes of

apportionment.’’ 119 S.Ct. at 777.

III. The Census Bureau’s Calculation of

Population for the Purpose of

Redistricting is Subject to Section 195’s

‘‘Feasib[ility]’’ Standard

Section 141(c) of the Census Act

permits the ‘‘officers or public bodies

having initial responsibility for the

legislative apportionment or districting

of each State’’ to submit to the Secretary

‘‘a plan identifying the geographic areas

for which specific tabulations of

population are desired.’’ The same

provision directs the Secretary to report

such ‘‘[t]abulations of population,’’ as

well as the ‘‘basic tabulations of

population’’ for States that have not

submitted a plan, within one year of the

decennial census date. It is clear that

these population tabulations are not

‘‘the determination of population for

purposes of apportionment of

Representatives in Congress among the

several States’’ (Section 195), and

therefore are subject to Section 195’s

directive that the use of sampling

‘‘shall’’ be authorized if ‘‘feasible.’’

To begin with, the population

tabulations supplied to the States

pursuant to Section 141(c) simply are

not made or used for purposes of

apportioning seats in the House of

Representatives among the States.

Section 141(c) makes clear that it relates

to tabulations for ‘‘legislative

apportionment or districting of each

State.’’ And a separate subsection of

Section 141—subsection (b)—governs

the ‘‘tabulation of total population by

States * * * as required for the

apportionment of Representatives in

Congress among the several States.’’

Indeed, the distinction between these

two groups of calculations is confirmed

by their different due dates: the latter set

of numbers must be completed three

months earlier than the redistricting

information required by Section 141(c).

See also Section 141(e)(2)

(distinguishing between use of census

data for ‘‘apportionment of

Representatives in Congress among the

several States’’ and for ‘‘prescribing

congressional districts’’).

Some commentators have suggested

that the term ‘‘apportionment’’ within

Section 195’s ‘‘[e]xcept’’ clause

encompasses population calculation for

the purposes of redistricting as well as

for the purpose of allocating seats in the

House of Representatives among the

States. That position is inconsistent

with the plain language of the statute.

First, it ignores the clear distinction in

Section 141 between these two

categories of calculations. Second,

Congress in 1976 revised the ‘‘[e]xcept’’

clause, replacing the word

‘‘apportionment’’ with the phrase

‘‘apportionment of Representatives in

Congress among the Several States.’’ It

is difficult to imagine how Congress

could have more clearly evidenced its

intent to limit Section 195’s prohibition

against the use of sampling to the

calculation of population used to

allocate among the States seats in the

House of Representatives. And because

Section 141(c) specifically refers to

tabulations for redistricting purposes,

but that reference does not appear in the

‘‘[e]xcept’’ clause of Section 195, it is

plain that redistricting tabulations are

not encompassed within the Section 195

prohibition. 3

Finally, some commentators have

suggested that as a practical matter these

two sets of numbers are inextricably

linked, asserting—for example—that it

would be a plainly improper result if

the Section 141(c) population tabulation

of a State for redistricting purposes did

not equal the Section 141(b)

apportionment population tabulation for

that State. Nothing in the Census Act

requires that result and, moreover, the

two totals have not been equal in the

past. For example, government

personnel stationed overseas are

included in a State’s Section 141(b)

tabulation, but are not included in the

data provided to that State under

Section 141(c). Congress could have

required such equality in either Section

141 or Section 195, but it did not do so.

Rather, Congress in Section 141

expressly distinguished between the

two categories of calculations.

The Census Act thus clearly directs

that statistical sampling ‘‘shall’’ be used

in tabulating population for the

purposes set forth in Section 141(c) if

the Secretary considers it ‘‘feasible’’ to

do so. Even if the plain language of the

Act were not clear on this point, we

believe that this interpretation is most

consistent with the purposes of the

Census Act and that adopting such an

interpretation is within your discretion.

In Wisconsin v. City of New York, 517

U.S. 1 (1996), the Supreme Court

unanimously concluded ‘‘the wide

discretion bestowed by the Constitution

upon Congress, and by Congress upon

the Secretary,’’ mandates substantial

judicial deference to the Secretary’s

determinations with respect to the

decennial census (517 U.S. at 19). Given

the long history of the use of sampling

by the Census Bureau, and the

importance of obtaining the most

accurate population tabulations

possible—because of the constitutional

significance of the ‘‘one person, one

vote’’ principle and of the equal

protection principles reflected in the

Voting Rights Act—interpreting the

statute to permit the use of sampling

when feasible is the most appropriate

approach. The alternative interpretation

would bar the use of statistical sampling

even if the use of sampling would lead

to more accurate results, a construction

that conflicts with the basic goal of the

decennial census—to obtain an accurate

count of the persons within the United

States.

IV. The Standard For the Feasibility

Determination

Section 195 does not contain a

definition of the term ‘‘feasible.’’ The

dictionary definition of the term ranges

from the most common ‘‘capable of

being done or carried out’’ to ‘‘capable

of being used or dealt with successfully,

suitable’’ or ‘‘reasonable, likely.’’

Webster’s Ninth New Collegiate

Dictionary (1990). The Supreme Court

has considered the word ‘‘feasible’’ in

other contexts and found that the plain

meaning of the term generally denotes

the first and broadest definition—

‘‘capable of being done.’’ In American

Textile Mfrs. Institute, Inc. v. Donovan,

452 U.S. 490, 509 (1981), the Court

interpreted the term ‘‘to the extent

feasible’’ to preclude the Secretary of

Labor from engaging in a cost-benefit

analysis of a public health standard; as

the Court explained, Congress itself, by

requiring a standard ‘‘to the extent

feasible’’ had made the policy choice for

the Secretary. See also Citizens to

Preserve Overton Park, Inc. v. Volpe,

401 U.S. 402, 411 (1971) (‘‘the

requirement that there be no ’feasible

38398 Federal Register / Vol. 65, No. 119 / Tuesday, June 20, 2000 / Notices

4Of course, in other contexts where there is no

independent requirement that the population court

be conducted without the use of sampling (unlike

the decennial census, where the statue as construed

by the Supreme Court prohibits the use of sampling

for apportionment of seat in the House of

Representatives), the analysis might also take

greater account of the efficiencies that could be

gained by substituting sampling for those other

methods.

alternative’ route admits of little

administrative discretion.’’).

We understand the term ‘‘feasible’’ in

accordance with its ordinary meaning

and the overall purposes of the Census

Act. It also must be understood in terms

of the uses to which non-apportionment

census data are put, including, among

other things, redistricting and allocation

of federal funds. While in other contexts

it might be appropriate to understand

‘‘feasible’’ to mean ‘‘possible,’’ given the

obvious importance of obtaining the

most accurate population (and other)

tabulations possible, it would seem

most appropriate to construe that term

in a manner that focuses upon

promoting accurate census results. 4

Thus, with respect to the proposed use

of statistical sampling for data to be

released to the States under Section

141(c), such use is ‘‘feasible’’ within the

meaning of Section 195 if (1) the

proposed use of sampling is compatible

with the other aspects of the census

plan, and with any statutory, timing,

and funding constraints; and (2) the

proposed use of statistical sampling

would improve the overall accuracy of

the census data.

The two components of ‘‘feasibility ‘‘

can be termed ‘‘operational feasibility’’

and ‘‘technical feasibility.’’ These are

matters that are properly within the

expert judgment of the Census Bureau.

The Census Bureau’s extensive

experience in the conduct of the census,

the use of statistical sampling

techniques, and the measurement of

accuracy should be the basis for these

essentially technical judgments.

V. The Decisionmaking Process

The determination whether the use of

sampling is ‘‘feasible’’ under Section

195 should be based upon the

information before the decisionmaker at

the time the determination is made.

Public Law No. 94–171 requires the

Census Bureau to deliver official census

data to the states for redistricting

purposes by April 1, 2001. 13 U.S.C.

141(c). As with every decennial census,

the Census Bureau will conduct

extensive analyses on the census data in

the ensuing years. In order to make a

final decision on whether to deliver

statistically corrected data for

redistricting purposes, the Census

Bureau need only consider the evidence

available to it at the time of its decision

to determine whether the statistically

corrected numbers are more accurate

and therefore that the use of sampling

is ‘‘feasible’’ as that term is defined

herein. See, e.g., Vermont Yankee

Nuclear Power Corp. v Natural

Resources Defense Council, 435 U.S.

519, 552–54 (1978) (review of agency

decision must be made based on

information available at the time the

decision was made); ICC v. New Jersey,

322 U.S. 503, 514 (1970).

The Census Bureau is in the process

of completing a document which will

provide information concerning its

assessment of whether using statistically

sampling is feasible with respect to the

release of P.L. 94–171 data. Although, as

the document will indicate, the Census

Bureau has determined that the use of

statistical sampling is operationally

feasible and should improve the

accuracy of the census, no final decision

will be made with respect to the release

of data until after the Bureau has had

the opportunity to review whether

census operations were conducted in a

way that met expectations. This

document will be published in the

Federal Register, along with a proposed

regulation that would delegate to the

Director of the Census the Secretary of

Commerce’s authority to make the final,

technical decision on what numbers to

release and would set forth a process for

the Census Bureau’s consideration of

what numbers to release.

Robert J. Shapiro,

Under Secretary for Economic Affairs.

[FR Doc. 00–15348 Filed 6–14–00; 8:45 am]

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