COMPARISON OF ACS AND ASEC DATA ON HOUSEHOLDS AND FAMILIES: 2004

Martin O'Connell

Gretchen Gooding

Population Division

U.S. Census Bureau

*This report is released to inform interested parties of ongoing
research and to encourage discussion of work in progress. The views
expressed on the statistical and methodological issues in this report
are those of the authors and not necessarily those of the U.S. Census
Bureau.*

COMPARISON OF ACS AND ASEC DATA ON HOUSEHOLDS AND FAMILIES: 2004

# INTRODUCTION 

This report is one in a series that compares data from the American
Community Survey (ACS) with data from the Annual Social and Economic
Supplement (ASEC) to the Current Population Survey (CPS). This report
focuses on comparisons of national distributions of household and family
characteristics, including household size and composition, relationship,
and marital status, between the 2004 ACS and the 2004 ASEC. In this
analysis, we compare the 2004 ACS and the 2004 ASEC distributions and
look for differences that are both statistically and substantively
different, and for those found, offer possible explanations.

# METHODOLOGY

The tables included in this report compare the most commonly tabulated
data on households, families, and marital status from the ACS and the
ASEC. Comparisons consist primarily of percentage-point differences
between the two distributions. Tables display the ACS and the ASEC
estimates, the margins of error from which 90-percent confidence
intervals of the estimates can be derived, and the difference between
the two estimates. In the case of frequency distributions, the
difference is calculated as the percent difference between the two
estimates. In the case of relative frequency distributions, the
difference is calculated as the percentage-point difference between the
two estimates. An asterisk (\*) denotes statistically significant
differences.

At the national level, the ACS and the ASEC variances were quite small,
resulting in many statistically significant differences between the ACS
and the ASEC distributions. In this report, we focus on statistically
significant differences of 0.5 percentage points or more. This yardstick
was developed to help focus the analysis, though it can vary based on
the relative size of the category. For example, for population groups
constituting a relatively large percentage of the population (for
example, spouses of the householder), a 0.5 percentage point difference
in the estimates might be small, while for population groups
constituting a smaller percentage of the population (for example,
siblings of the householder), a 0.5 percentage point difference could be
quite large. This decision is subjective, however, and users can apply
their own standards to interpret the data presented in this report.

The remainder of this section examines differences in methodology
between the two surveys.

# 

# Sample Frame

The 2004 ACS surveyed a national sample of housing units, both occupied
and vacant. Data were collected in a total of 1,235 counties out of the
3,141 counties in the United States. The sample is designed to provide
estimates of housing and socio-economic characteristics for the nation,
all states, most areas with a population of 250,000 or more, and
selected areas of 65,000 or more.

The 2004 ASEC surveyed a national sample of households. The sample is
designed primarily to produce estimates of the labor force
characteristics of the civilian noninstitutionalized population 16 years
of age and older for the nation and all states.

One difference between the two survey universes is that the ASEC
includes a small number of individuals living at addresses that were
housing units in 2000 but have since been converted into
noninstitutional group quarters (e.g. emergency and transitional
shelters and group homes). For the purposes of this report, all
individuals with detailed household and family status of "in group
quarters" (HHDFMX = 51) were excluded from the ASEC estimates.

# Sample Size and Mode of Data Collection

The 2004 ACS interviewed a total of 534,383 households. Data were
collected continuously throughout the year using a combination of
mail-out/mail-back questionnaires, Computer-Assisted Telephone
Interviewing (CATI), and Computer-Assisted Personal Interviewing (CAPI).
Each month a unique national sample of addresses received an ACS
questionnaire. Addresses that did not respond were telephoned during the
second month of collection if a phone number for the address was
available, and personal visits were conducted during the third and last
month of data collection for a subsample of the remaining nonresponding
units. The 2004 ACS achieved an overall survey response rate, calculated
as the initially weighted estimate of interviews divided by the
initially weighted estimate of cases eligible to be interviewed, of 93.1
percent.

The 2004 ASEC contained interviews from about 77,000 households and 59
noninstitutional group quarters. The ASEC interviews were collected over
a three-month period in February, March, and April 2004 as a supplement
to the basic monthly CPS conducted during those months, with most of the
data collected in March. All ASEC data are collected via
Computer-Assisted Telephone and Personal Interviews (CATI/CAPI), with
interviews conducted during one week each month. The response rate for
the 2004 ASEC was 91.8 percent. Response rates among eligible households
were about 92 percent in February and April 2004 and 91 percent in March
2004.

Both the ACS and ASEC employ experienced permanent interviewers for CATI
and CAPI data collection.

# Residence Rules

The ACS and the ASEC employ different residence rules to determine which
individuals in a household are eligible for interview; the ACS uses the
concept of current residence, while the ASEC uses a version of usual
residence. This difference may contribute to variation in the universes
on which social characteristics depend.

The ACS interviews everyone in the housing unit on the day of interview
who is living or staying there for more than two months, regardless of
whether or not they maintain a usual residence elsewhere, or who does
not have a usual residence elsewhere. If a person who usually lives in
the housing unit is away for more than two months at the time of the
survey contact, he or she is not considered to be a current resident of
that unit. This rule recognizes that people can have more than one place
where they live or stay over the course of a year, and these people
affect that estimate of the characteristics of the population for some
areas.

The ASEC interviews everyone staying in the housing unit at the time of
the interview who considers the housing unit as their usual residence or
who has no usual residence elsewhere. In addition, the ASEC also
includes temporarily absent individuals who consider the housing unit as
their usual residence.

The different residence rules result in a notable difference in the
universe of the two surveys. Because the 2004 ACS excluded group
quarters from the sample frame and interviewed individuals at their
current residence, college students living in dormitories are not
included in the ACS universe. In contrast, the ASEC interviewers are
instructed to include as household members any college students who are
temporarily absent from the household, including those who are currently
residing in college dormitories. The result is that the ASEC sample
universe should include more college students than the ACS sample
universe.

# Question Wording 

# Differences between the ACS and the ASEC in presentation and wording of questions may contribute to differences in estimates. 

# Relationship. The current version of the 2004 American Community Survey asks the relationship item as follows:

How is this person related to Person 1?

(Person 1 is the person living or staying here in whose name this house
or apartment is owned, being bought, or rented. If there is no such
person, start with the name of any adult living or staying here.)

Relationship of Person X to Person 1,

Husband or wife

Son or daughter

> Brother or sister
>
> Father or mother
>
> Grandchild
>
> In-law
>
> Other relative
>
> Roomer, boarder
>
> Housemate, roommate
>
> Unmarried partner
>
> Foster child
>
> Other nonrelative

The current version of the 2004 ASEC asks the relationship item as
follows:

(I am going to read a list of relationship categories.)

How (are/is) (name/you) related to (name of reference person)?

> Spouse (Husband/Wife)
>
> Unmarried Partner
>
> Child
>
> Grandchild
>
> Parent (Mother/Father)
>
> Brother/Sister
>
> Other relative (Aunt, Cousin, Nephew, Mother-in-law, etc.)
>
> Foster child
>
> Housemate/Roommate
>
> Roomer/Boarder
>
> Other nonrelative

Including the category "Householder," the ACS has 13 relationship
categories, and the ASEC has 12. The one extra category is "In-law." Not
all categories are worded the same way in the two surveys, and the
ordering of the categories changes after the first response. These
differences in wording and ordering may account for differences in
reporting between the two surveys.

**Marital Status.** For the marital status item, the ACS asks each
respondent about their current marital status, giving them 5 possible
options:

What is this person's marital status?

Now married

Widowed

Divorced

Separated

Never married

The ASEC questionnaire offers 6 possible options, further specifying
whether a married person has his or her spouse present or absent:

(Are/Is) (name/you) now married, widowed, divorced, separated or never
married?

> Married spouse present
>
> Married spouse absent
>
> Widowed
>
> Divorced
>
> Separated
>
> Never married

In instances where respondents indicate that they are married with their
spouse present, a further question in the ASEC asks for the
identification of the spouse.

**Family Relationships.** The level of detail collected in the
relationship information differs between the two surveys, causing
differences in areas such as the linkage of spouses to each other and of
children to parents, routines that form the basis for identifying
different types of households. In the ACS, relationship is identified
only by a person's relationship to the householder. The derivation of
subfamilies (combining different people into married-couple or
single-parent subfamilies) in the ACS is accomplished indirectly, using
the relationship-to-householder item in conjunction with a person's
marital status.[^1] For example, in the ACS, if a child of the
householder over 15 years old and a grandchild are living in the same
household, it is assumed that the child and the grandchild are actually
biologically related to each other and form a single-parent family if
their age difference is appropriate.

In the ASEC, specific parent and child pointers directly ascertain if
this is a parent-child subfamily group. Spouse pointers also better
identify married couples in the ASEC. In addition, directly asking
householders if they are currently married and living with their spouse
may provide better estimates of married-couple households in ASEC data
than in ACS data, where the relationship item is the sole source for
identifying these households. For these reasons, distributions
identifying married-couple households and married-couple subfamilies or
children in subfamilies may differ depending on whether they are based
on ACS or ASEC data.

# Item Nonresponse

Item nonresponse is the failure of an individual to provide complete and
usable information for a data item. Item allocation rates are often used
as a measure of the level of item nonresponse. These rates are computed
as the ratio of the number of eligible people or households for which a
value was allocated during the editing process for a specific item to
the number of people or households eligible to have responded to that
item.

For the 2004 ACS, allocation rates for the relationship and marital
status items were 0.8 percent and 1.1 percent, compared with 1.6 percent
and 2.5 percent for the 2004 ASEC. [^2]

# Data Editing and Imputation Procedures

# ACS and ASEC edit and imputation rules are designed to ensure that the final edited data are as consistent and complete as possible. These rules are used to identify and account for missing, incomplete, and contradictory responses. In each case where a problem is detected, pre-established edit rules govern its resolution.

The ACS and the ASEC employ two principal imputation methods: relational
imputation and hot deck allocation. Relational imputation assigns values
for blank or inconsistent responses on the basis of other
characteristics on the person's record or within the household. Hot deck
allocation supplies responses for missing or inconsistent data from
similar responding housing units or people in the sample.

Both ACS and ASEC editing procedures employ logical checking routines to
produce consistency among household members. For example, spouses of
householders, as well as the householders themselves, must be "Now
married," and there can be only one spouse of the householder. Parents
must be at least 12 years older than their children and a householder
cannot have both a spouse and an unmarried partner. Allocation routines
using hot decks generally stratify the donors and the recipients of the
hot deck by their age, sex, race, and other characteristics of the
household.

# 

# Controls and Weighting 

# Notable differences in the selection of controls and the calculation of weights between the two surveys may lead to differences in estimates. The ACS and the ASEC are both weighted to account for the probability of selection and housing unit nonresponse. 

## After the initial weighting, data from the ACS and the ASEC are both controlled to be consistent with independent population estimates. Data from the 2004 ACS are controlled, at the county level, to independent estimates of the household population and housing units in July 2004. The 2004 ASEC is controlled to independent national estimates of the civilian non-institutionalized population in March 2004. The ASEC totals include this population and also members of the Armed Forces living off post or with their families on post if at least one civilian adult lives in the household. In addition, the ACS presents the average responses over a 12-month period, while the ASEC shows the living arrangements of people for the February-April time period, although the population is controlled to March estimates. Because the ACS controls to both the total population and the total number of housing units, the ACS files contain both person weights and housing unit weights. The ASEC does not control to the total number of housing units and, thus, the ASEC files do not contain an independent housing unit weight but instead use the weight of the householder as the weight of the housing unit.

After the application of the controls, the ASEC data are raked to ensure
that the number of husbands and wives are equal and that the number of
married couple households equals the number of married householders. The
ACS employs no similar raking.

# RESULTS

# Households by Type and Presence and Age of Own Children

Table 1 presents data on "Households by Type and Presence and Age of Own
Children." Although most of the percent differences are relatively
small, three differences draw this paper's further examination: the
proportion of households that are family households, the proportion that
are married-couple families, and the proportion with their own children
under 18 years. The ACS shows lower proportions for all categories (67.2
percent, 50.2 percent, and 22.1 percent, respectively) than the ASEC
(68.1 percent, 51.5 percent, and 23.0 percent). These differences are in
part due to differing levels of detail collected about relationship
information. The ACS uses a single relationship item to establish the
relationship of the householder to other household members. As explained
earlier, the ASEC uses specific parent and child pointers to ascertain
precise relationships between household members, as well as to elicit a
detailed response in the marital status item to identify householders
who are not only married but also living with a spouse in the household.
For reasons such as these, the ACS and the ASEC differ in distributions
related to married couples or children in different types of families.

The ACS data also show a relatively higher proportion of nonfamily
households than the ASEC data (32.8 percent and 31.9 percent,
respectively).

## **Number of Households.** To estimate the number of occupied households, the ACS uses the housing unit weight, while the ASEC uses the individual weight of the person who is identified as the "householder" (the person in whose name the housing unit is owned or rented), thus assuring consistency in the numbers of householders and occupied households. The ACS number, although controlled to an independent estimate of the number of occupied housing units, will differ from the number of householders (109.9 million households but 113.4 million householders in 2004). Differences in average household and family sizes between the two surveys for 2004 may also be the result of these weighting procedures or differences in the way family relationships are established in the editing phase of the surveys.

**Households by Type and Size**

Table 2 examines "Households by Type and Size." While the percentage
differences for the individual size-distribution categories between the
two surveys are 0.5 percent or less, statistically significant
differences are noted for the estimates of both average household size
and average family size. For both estimates, the ACS records higher
average household and family sizes. These differences may result from
different maximum allowable sizes: the ACS allows up to 20 people, while
the ASEC allows 16.

**Households by Opposite Sex Unmarried Partners**

Table 3 looks at "Opposite Sex Unmarried Partner Households by Sex of
Householder." The proportion of opposite sex, unmarried-partner
households among all households in the ACS is 4.7 percent, compared with
4.2 percent in the ASEC. Perhaps the presence or absence of an
interviewer may affect the response patterns for this question. If so,
the absence of an interviewer yields the higher incidence of unmarried
partner households found in the ACS.

**Relationship to Householder by Household Type**

Table 4, "Relationship to Householder by Household Type," shows that the
proportion of people who are children of the householder is found to be
lower in the ACS (29.8 percent) than in the ASEC (30.6 percent).[^3]
This difference is consistent with data in Table 1, which shows that the
proportion of married-couple households with children is lower in the
ACS (22.1 percent) than in the ASEC (23.0 percent). As previously noted,
the availability of differing levels of detail about relationships most
likely explains why distributions vary between the ACS and the ASEC. In
addition, a higher proportion of male family householders are found in
the ACS than in the ASEC (15.8 percent and 14.6 percent, respectively),
and conversely, a lower proportion of female family householders (11.0
percent and 11.8 percent, respectively). Again, the ASEC interviewing
structure\--requiring personal or telephone contact between respondent
and interviewer for all households\--may produce this result. (Personal
or telephone contacts in the ACS are made only for follow-up
nonrespondent households). As wives are less likely than husbands to be
in the labor force and more likely to be at home when the interviewer
calls, one would expect married-couple households in the ASEC to
evidence relatively more female family householders due to the wife
answering for the household and the interviewer recording her as the
householder in the case of jointly owned or rented housing. ASEC
interviewers are instructed to place as "Person One" (the householder)
the person to whom they are speaking in the case of jointly owned or
rented housing.

**Estimates of Own and Related Children**

The ACS and the ASEC differ in their estimates of "own child" in Table 5
for the population under 18 years. While the overall difference for the
"Own child" category between the two surveys is -0.7 percentage points,
the ASEC shows a higher percentage of own children in married-couple
families than does the ACS (66.2 percent and 63.9 percent,
respectively). Conversely, the ACS shows a higher percentage of own
children residing in other family types than the ASEC (25.0 percent and
23.4 percent, respectively). These differences may reflect differing
levels of detail in collecting marital status and relationship
information and different methods of classifying families as married.
The ACS uses a single relationship item to establish the relationship of
the householder to other household members. The ASEC uses specific
parent and child pointers to ascertain more precise relationships
between household members. In addition, more detailed marital status
categories identifying spouses as being present and spouse pointers that
better identify married couples in the ASEC may account for this
difference. Also noted in Table 5 is a larger percentage of children in
the ACS listed as grandchildren of the householder (6.5 percent) than in
the ASEC (5.5 percent).

**Subfamilies**

In Table 6, "Subfamily Type by Presence and Age of Own Children Under
18," 31.1 percent of all subfamilies in the ACS are married-couple
subfamilies, compared with 39.4 percent in the ASEC. The ACS has lower
percentages than the ASEC of married-couple subfamilies either with
their own children (14.0 percent and 17.3 percent, respectively) or
without their own children (17.1 percent and 22.1 percent,
respectively). As a result, the ACS has a higher percentage of
single-parent, father-child subfamilies than does the ASEC (17.1 percent
and 8.9 percent, respectively). These differences may be due to the
differing levels of detail in collecting relationship information, as
explained above.

**Marital Status**

Overall, most differences in the percentage distribution of males and
females by marital status in Table 7 are 0.5 percentage points or less.
One exception is the lower proportion of never-married men in the ACS
(14.8 percent) than in the ASEC (15.8 percent). In 2003, the difference
was 0.8 percentage point (14.7 percent for the ACS compared with 15.5
percent for the ASEC). This disparity may be due to the inclusion in
ASEC households of people who live in college dormitories but are also
reported as household members by householders who maintain a room for
them in their absence. As the majority of college-age people have never
married, this reporting could potentially increase the difference
between the proportion of never-married people in the ASEC and that in
the ACS. In addition, differences may also be due to the presence or
absence of an interviewer to aid respondents. The majority of responses
from ACS households are from mail-out/mail-back forms whereby
respondents are able to see a list of possible responses to the marital
status item (Now married, Widowed, Divorced, Separated, or Never
married). On the other hand, data collection for ASEC is done via
interviewer/respondent mode, either in-person or by telephone, so
respondents are not able to see possible response categories. The ASEC's
mode of data collection could cause a response of "single" to be
recorded as "never married," when in reality it could mean living alone.

# SUMMARY

Data from the American Community Survey (ACS) on families, households,
and the marital status of the population are consistent with those from
the Annual Social and Economic Supplement to the Current Population
Survey (ASEC). The principal differences noted in this paper are the
larger proportion of married couples and own children of the
householders in the ASEC and the larger proportion of nonfamily
households in the ACS. Some of these differences can be traced to the
different collection and editing procedures used to identify and link
spouses and children with parents. In addition, the different weighting
procedures used in the two surveys to estimate the number of households
must be considered in any analysis of the household data and living
arrangements tabulations.

[^1]: A subfamily consists of either a married couple or a single
    parent-child family whose members are related to the householder but
    are not either the householder or his/her spouse.

[^2]: The universe for the marital status item was the population 15
    years and older.

[^3]: For population tables shown in this report, the person weights of
    individuals are used in both the ACS and the ASEC. While the number
    of family householders on the ASEC is the same in Tables 1 and 4
    (76.2 million), the number of family householders in the ASEC is
    73.9 million when using the housing weight in Table 1 and 76.5
    million when using the person weight in Table 4.