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Disability Variables in the American Housing Survey
A M E R I C A N H O U S I N G S U R V E Y
DISABILITY VARIABLES IN THE
AMERICAN HOUSING SURVEY
U.S. Department of Housing and Urban Development | Office of Policy Development and Research American Housing Survey
Disability Variables in the
American Housing Survey
Prepared For:
U.S. Department of Housing & Urban Development
Office of Policy Development & Research
Prepared By:
Frederick J. Eggers & Fouad Moumen
Econometrica, Inc.
Bethesda, Maryland
Contract No. C-CHI-01030
Order No. CHI-T0001
Project No. 1031-000
November 2011
Table of Contents
Executive Summary ...................................................................................................... v
Introduction ................................................................................................................... 1
The Concept of Disability ............................................................................................. 1
Disability and Large-Scale Statistical Surveys ........................................................... 3
Surveys Focusing on Health and Disability ................................................................ 3
Surveys Reporting Disability Information in a Non-Health Context ............................ 4
Choosing Among the Surveys ..................................................................................... 7
AHS and Person-Level Information on Disabilities..................................................... 7
AHS and Household-Level Information of Disabilities ................................................ 8
Disabilities at the Household Level: AHS vs. ACS ..................................................... 9
Housing Characteristics of Households with Persons with Disabilities ................ 13
Relationship among AHS Household-Level Disability Variables ............................ 20
Statistical Analysis ................................................................................................... 20
Conceptual Analysis ................................................................................................ 22
Summary of Surveys’ Characteristics and Guidance on Their Use ........................ 27
Appendix A ................................................................................................................ A-1
Appendix B ................................................................................................................ B-1
iii
List of Tables and Figures
Table ES-1: Summary of Key Characteristics of Surveys Using Standard Questions on
Disabilities..................................................................................................vi
Figure 1:
ACS Questions on Disabilities ...................................................................... 5
Table 1:
2009 Population Counts from the AHS and ACS ......................................... 7
Table 2:
Differences in Housing Counts, AHS vs. ACS .............................................. 9
Table 3:
Comparison of Household Level Information on Disabilities: 2009 AHS vs.
ACS ............................................................................................................ 10
Table 4:
Incidence of Disability by Household Size .................................................. 13
Table 5:
Households with Disabilities, by Number of Members with a Disability ...... 14
Table 6:
Households with Disabilities, by Disability Type ......................................... 15
Table 7:
Housing Characteristics and Household Income for Households with
Members with Disabilities ........................................................................... 16
Table 8:
Correlations among the AHS Household-Level Disability Variables ........... 20
Table 9:
Principal Components for the Six Household-Level Disability Variables .... 21
Table 10: Relationship between Any Disability and the Specific Disabilities .............. 22
Table 11: Relationship among Disabilities at the Household Level ............................ 25
Table 12: Summary of Key Characteristics of Surveys Using Standard Questions on Disabilities .................................................................................................. 28
Table A-1: Comparison of Person Level Information on Disabilities: 2009 AHS vs.
ACS............................................................................................................ A-2
Table A-2: Demographic Characteristics of Individuals with Disabilities, AHS vs.
ACS............................................................................................................ A-3
Table A-3: Relationship among Disabilities at the Person Level, AHS vs. ACS ..........A-4
Table A-4: Correlation Matrices among the Disability Variables, AHS vs. ACS ..........A-5
Table B-1: Counts of Persons with Disabilities 15 Years Old or Older –
CPS, AHS, and ACS .................................................................................B-1
iv
Executive Summary
The 2009 American Housing Survey (AHS) included, for the first time, a battery of six questions on whether occupants suffer from disabilities. The six questions were taken from the American Community Survey (ACS), and the same six questions are used in the Current Population Survey (CPS) and the Survey of Income and Program Participation (SIPP). The National Health Interview Survey (NHIS) and selected supplements to SIPP contain more detailed questions on disabilities and related health conditions. This paper compares the various surveys that use the ACS questions and analyzes the data from the 2009 AHS on disabilities.
Table ES-1 describes the key features of the AHS, ACS, CPS, and SIPP with respect to the questions on disabilities. The AHS is the only survey that tabulates the data at the household level and that provides both person-level and household-level variables in its public use file; the other surveys tabulate data at the person level and contain only person-level variables in their public use file. The AHS does not provide person-level weights and, while the housing unit weights can be used to weigh occupants, they produce smaller counts than the counts based on person weights in the other surveys. The AHS and ACS ask the questions of the same populations, but the CPS and SIPP ask the questions only of persons 15 years old or older.
Comparisons of both person-level and household-level tabulations from the AHS and the ACS
reveal that the percentages of persons and households affected by disabilities are substantially lower in the AHS than in the ACS. Neither the Census Bureau nor independent researchers have systematically examined these differences. The two most plausible explanations availabl e at this point are: (1) the ACS asks the full battery about each person in the household, whereas the AHS
asks the full battery about household members only if the respondent answers positively to a question about whether anyone in the household has a disability and (2) the ACS mail questionnaire is more private than the AHS’ telephone interview and therefore might elicit fuller answers to sensitive questions. Appendix B compares the AHS, the ACS, and the CPS on counts and incidence for persons 15 years old and older. All the CPS percentages are higher than those of the AHS and lower than those of the ACS. In every case, the CPS percentage is closer to the AHS percentage than to the ACS percentage. The recent HUD report on Worst Case Housing Needs of People with Disabilities found that the AHS and the NHIS produced similar estimates for similar disability concepts. The percentage differences between the AHS and the ACS are important and need further analysis.
Because the AHS does not provide person-level weights, the text uses the AHS data to analyze the prevalence of disabilities only at the household level. Appendix A analyzes disabilities at the person level using both AHS and ACS data.
The six questions fall into two groups. Four questions inquire about specific impediments: difficulty walking or climbing stairs, difficulty with memory or general cognition, difficulty hearing, and difficulty seeing. The remaining two questions examine whether a member of the household is restricted in his or her ability to function at home (namely, whether the person is able to bathe or dress without assistance) and to function outside the home (namely, the ability to v
Table ES-1: Summary of Key Characteristics of Surveys Using Standard Questions on Disabilities Features ACS AHS CPS SIPP
Standard questions on
Hearing, seeing, walking,
Hearing, seeing, walking,
Hearing, seeing, walking,
Hearing, seeing, walking,
disabilities
memory, bathing and
memory, bathing and
memory, bathing and
memory, bathing and
dressing, running errands
dressing, running errands
dressing, running errands
dressing, running errands
Additional questions
None
None
Effect of disabilities on
Six questions and question
labor force participation
on effect of disabilities on
labor force participation in
one or more common
topical modules;
additional questions that
provide more detail on
conditions related to
disability are asked in
topical modules on an
irregular basis
vi
Data
collected
Person-level Person-level Person-level Person-level
Public use file variables
Person-level only
Person- and household-
Person-level only
Person-level only
level
Weights
Person and housing unit
Housing unit only
Person and housing unit
Person and housing unit
Published tabulations
Person-level—includes
Household-level
Person level—labor force
No regular tables
(includes Internet tables)
labor force participation
participation-related
published, special reports
by disability
issues only
available online
run errands, such as go to the doctor or shop). Viewed this way, four questions identify the causes of a disability, and two questions measure its severity.
From the perspective of four questions i dentifying impediments and two questions measuring severity, the key findings are:
1. The number of households where one or more members has a disability that prevents him or her from performing functions inside or outside of the house is considerably smaller than the number of households where one or more members has one or more disabilities.
a. There are 19,182,000 households that have one or more members with a disability. This is 17.3 percent of all households.
b. There are 6,206,000 households that have one or more members who have difficulty performing functions outside of the house; that is, running errands, such as visiting a doctor or shopping.
c. There are 2,969,000 households that have one or more members who have difficulty performing functions inside the house, such as bathing or dressing.
d. Taking into account the overlap between having difficulty performing functions (inside and outside of the house), there are 6,847,000 households where one or more member has a disability that prevents him or her from performing functions inside or outside of the house. This is 6.1 percent of all households.
2. At the household level, difficulty performing inside or outside of the house rarely occurs independently of other disabilities.
a. Only 7.3 percent of households that report having a member who experiences difficulty performing functions outside of the house report no other disability among household members.
b. Only 2.2 percent of households that report having a member who experiences difficulty performing functions inside the house report no other disability among household members.
3. At the household level, having difficulty performing functions outside of the house is more commonly the result of having other disabilities than of having difficulty with bathing or dressing, and having difficulty with bathing or dressing rarely occurs without having difficulty performing errands.
a. Households where one or more members has difficulty performing functions outside of the house total 6,206,000, compared to 2,969,000 households that have members who have difficulty performing functions inside the house.
b. Only 64,000 households have members who have difficulty performing functions inside the house but have no members who have difficulty performing functions outside of the house.
4. At the household level, having difficulty walking or climbing stairs is the disability most commonly associated with having difficulty performing functions inside or outside of the house.
a. Of the households that have one or more members with difficulty bathing or dressing, 89.1 percent have one or more members with difficulty walking.
vii
b. Of the households that have one or more members with difficulty running errands, 70.7 percent have one or more members with difficulty walking.
5. At the household level, having difficulty with memory or cognition is the second most common disability associated with having difficulty performing functions inside or outside of the house.
a. Of the households that have one or more members who have difficulty with bathing or dressing, 47.5 percent have one or more members who have difficulty with memory.
b. Of the households that have one or more members who have difficulty running errands, 42.4 percent have one or more members who have difficulty with
memory.
6. At the household level, difficulty with hearing or seeing are infrequently associated with the ability to perform functions inside or outside of the house.
a. Among households with one or more members who have difficulty with bathing or dressing, only 27.6 percent have members with difficulty hearing, and only 18.7 percent have members with difficulty seeing.
b. Among households with one or more members who have difficulty running errands, only 25.1 percent have members with difficulty hearing, and only 18.7
percent have members with difficulty seeing.
Analysis in Appendix A confirms—with both AHS and ACS data—that these same relationships hold at the person level.
There are clear patterns in the incidence among households; these patterns are very similar for each of the conditions identified by the six questions and for having any of the six conditions.
The most important findings are:
1. Among households with one or more members with a disability, 86 percent have only one member with a disability.
2. One-third of all households with disabilities are one-person households.
3. Among units in different structure types, the incidence of disabilities is highest among households living in mobile homes. The age of the occupants and household income probably account for this result.
4. Households in non-metropolitan areas have higher percentages of persons with disabilities than households in metropolitan areas. Generally, households in urban suburbs have the lowest percentages; this is not true for all of the specific disabilities, but these exceptions are statistically insignificant.
5. The incidence of households with members with disabilities is greatest among households living in units built prior to 1970 and is lowest for households living in units built in 1990 or later.
viii
6. The incidence patterns associated with household income are the most revealing. The percentage of households with one or more members with any disability among households who have extremely low incomes (30.6 percent) is more than three times greater than the percentage among households who have extremely high incomes (9.8
percent). The percentages decline monotonically across the income categories. This monotonic pattern is repeated in each of the specific disability categories except for a blip among the percentages for households with one or more members with a seeing disability. The income patterns appear to be related in straightforward ways to other patterns in the data. Having a member with a disability limits the income earning potential of any household but especially one-member households. Appendix A shows that the probability of an individual having a disability increases substantially with age.
Households over 59 (and particularly those over 74) have lower earned income and lower income in general.
7. This income pattern is reflected clearly in three of the four categories that involve the quality and affordability of housing.
a. The percentage of households with disabilities is much higher among those renter households that live in assisted housing than among those living in market housing.
b. The incidence of disability among households also varies systematically with rent burden—the ratio of housing costs to income. The percentages increase
monotonically as the severity of rent burden increases. This monotonic pattern is consistent across the various specific disabilities except for a blip in the percentages for difficulty with hearing.
c. While the overwhelming majority of housing units are considered adequate using the AHS adequacy measure, units that are moderately or severely inadequate have higher incidence levels.
d. Overcrowding, however, is not associated with disability. In fact, the incidence of disabilities declines with the number of persons per room. This is not surprising, since one-third of households with disabilities are one-person households; these households, by definition, cannot be overcrowded (i.e., have more than one person per room).
The paper concludes with recommendations to researchers about which survey to use depending upon how they want to incorporate information on disabilities into t heir research. These recommendations are tentative because of the unresolved issue about differences between the AHS and the ACS in the incidence of disability at the person and household levels.
ix
Disability Variables in the American Housing Survey
Disability Variables in the American Housing Survey
Introduction
In October 2009, Econometrica, Inc., entered into a contract with the U.S. Department of Housing and Urban Development (HUD) to support the American Housing Survey (AHS). Task 8 of that contract required the Econometrica team to analyze the information collected in the 2009 national AHS on disability. HUD asked Econometrica to summarize the AHS findings, to compare them with surveys with similar questions, and to provide guidance to AHS data users on how to interpret these variables.
In 2009, HUD and the Census Bureau included questions on disability in the AHS survey for the first time. The AHS asks a battery of six questions, the content and wording of which are based on the questions contained in the American Community Survey (ACS). The questions are asked at the person level, and the answers are tabulated at both the person and housing unit level. The Current Population Survey (CPS) and the Survey of Income and Program Participation (SIPP) also report disability status and use questions based on the ACS questions. Researchers studying disability per se would most likely use the much more extensive battery of questions contained in the National Health Interview Survey (NHIS), conducted by the Census Bureau for the Centers for Disease Control and Prevention (CDC).
The remainder of this report consists of seven sections:
• An overview of the disability concept.
• A comparison across surveys of the questions asked about disability status.
• A discussion of how to choose among the various sources of information on disability.
• A comparison of AHS tabulations at the housing unit level with tabulations in other surveys.
• Characteristics of households with members with disabilities from the AHS.
• Patterns in the AHS disability data at the household level.
• A summary comparison of the surveys and recommendations on choice among the surveys.
Appendices contain additional tabulations.
• Appendix A: Comparison of AHS tabulations at the person level with ACS tabulations.
• Appendix B: Comparison of CPS tabulations with AHS and ACS tabulations for persons 15 years old or older.
The Concept of Disability
A “disability” arises when an “impairment” (such as blindness or Alzheimer’s disease) limits a person’s ability to carry out a function (such as bathing or dressing) or to participate in an activity (such as employment). It is important to distinguish between the impairment and its effects and to remember that the effects of an impairment are dependent upon the environment.
For example, the ability of a near-blind person to work may depend upon the existence of special transportation facilities and the availability of special reading devices.
The World Health Organization (WHO) maintains two internationally accepted classification systems: the International Classification of Diseases (ICD) and the International Classification of Functioning, Disability and Health (ICF). The ICF, which was approved by member states in 2001, is designed to work in consort with the ICD. A useful discussion of the ICF model is contained in a paper on disability statistics in the NHIS.
… we adopt ICF concepts to create operational definitions of disability. The concepts used include impairment, activity limitation, participation restriction, and disability (see WHO, 2001). A prerequisite to e ach of these concepts is the presence of a health condition. Examples of health conditions are listed in the International Classification of Diseases, Tenth Edition (ICD-10) and they encompass diseases, injuries, health disorders, and other health related conditions. An impairment is defined as a significant deviation or loss in body function or structure. For example, the loss of a limb or vision loss may be classified as impairments. In some surveys, impairments are defined as long lasting health conditions that limit a person’s ability to see or hear, limit a person’s physical activity, or limit a person’s mental capabilities. An activity limitation is defined as a difficulty an individual may have in executing activities. For example, a person who experiences difficulty dressing, bathing or performing other activities of daily living due to a health condition may be classified as having an activity limitation. In some surveys, activity limitations are identified based upon a standard set of activities of daily living questions (ADLs) and/or instrumental activities of daily living questions (IADLs). A participation restriction is defined as a problem that an individual may experience in involvement in life situations. For example, a working-age person with a severe health condition may have difficulty participating in employment as a result of the physical environment (e.g., lack of reasonable employer accommodations) and/or the social environment (e.g., discrimination). In some surveys, participation restrictions are identified by questions that ask whether the person has a long lasting health condition that limits his or her ability to work, or whether a health conditions affects his or her ability to go outside his or her home to go shopping, to church or to the doctor’s office.
The final ICF concept that we use is a disability. The term disability is used to describe the presence of an impairment, an activity limitation and/or a participation restriction. This concept is similar to the definition used in the Americans with Disabilities Act of 1990 (ADA). The ADA defines a disability as “a physical or mental impairment that substantially limits one or more of the major life activities, a record of such an impairment, or being regarded as having such an impairment.”1
Cornell University’s Rehabilitation Research and Training Center on Disability Demographics and Statistics has prepared a series of papers on disability statistics in major surveys. While this series does not as yet contain an analysis of disability statistics in the AHS, readers will find on 1 Benjamin H. Harris, Gerry Hendershot, and David C. Stapleton, A Guide to Disability Statistics from the National Health Interview Survey, Rehabilitation Research and Training Center on Disability Demographics and Statistics, Cornell University, October 2005, pages 6-7.
this Web site user guides that evaluate the disability data found in the ACS, CPS, decennial census, NHIS, NHIS disability supplement, Panel Study of Income Dynamics, and SIPP.2
Readers should also be aware of a study by Mathematica Policy Research, Inc., funded by the Department of Health and Human Services.3 While not as detailed as the Cornell studies, this report examines a larger number of surveys, including the AHS. It cites supplemental questions within the AHS on disabilities in 1978 and 1995.
Disability and Large-Scale Statistical Surveys
Surveys Focusing on Health and Disability
Researchers who are interested in studying the causes and consequences of disabilities should rely mainly on the National Health Interview Survey. The NHIS dates back to 1957; it is conducted annually by the Census Bureau for the National Center for Health Statistics (NCHS),
which is part of the CDC.4 Currently, the survey collects data on approximately 87,500 persons from a representative sample of 35,000 households. Si nce 1997, the NHIS has had four core components: Household, Family, Sample Adult, and Sample Child.5
The Household component collects limited demographic information on all of the individuals living in a particular house. The Family component verifies and collects additional demographic information on each member from each family in the house and collects data on topics including health status and limitations, injuries, health care access and utilization, health insurance, and income and assets. The Family Core component allows the NHIS to serve as a sampling frame for additional integrated surveys as needed.
From each family in the NHIS, one sample adult and one sample child (if any children are present) are randomly selected, and information on each is collected with the Sample Adult Core and the Sample Child Core questionnaires. Because some health issues are different for children than they are for adults, these two questionnaires differ in some items, but both collect basic information on health status, health care services, and health behaviors.
The most recent description of the NHIS questionnaire applies to the 2010 NHIS. The Family Core component of the 2010 NHIS produced person-level variables for all household members.
A Health Status and Limitation of Activity section focused on disabilities.
For each family member (with some exclusions for children and youth), information is collected on activity limitations, including questions about work limitations; the need for personal assistance with personal care needs, such as eating, bathing, dressing, and getting around inside the home; and the need for personal assistance with handling routine needs, such as everyday household chores, doing necessary business, and shopping or running errands. If any limitations 2 http://www.ilr.cornell.edu/edi/disabilitystatistics/sources-userGuides.cfm#nhis.
3 Gina Livermore, Denise Whalen, Sarah Prenovitz, Raina Aggerwal, and Maura Bardos, Disability Data in National Survey, Center for Studying Disability Policy, August 22, 2011.
4 Information on the NHIS was drawn from its Web site: http://www.cdc.gov/nchs/nhis/about_nhis.htm#content.
5 A special supplement on disability was added to the 1994 and 1995 NHIS surveys; see
http://www.cdc.gov/nchs/nhis/nhis_disability.htm.
are identified, the respondent is asked to specify the health condition(s) causing the limitation(s) and indicate how long he or she has had each such condition.
More detailed information on disabilities is collected for the Sample Adult and the Sample Child.
The following description of the relevant section of the Sample Child questionnaire indicates the extent of information collected.
The Child Conditions, Limitation of Activity, and Health Status Section (CHS) of the 2009
NHIS contains information on conditions, limitations of activity, health status, and mental health.
The CHS includes questions on the following health conditions: mental retardation, developmental delays, Attention Deficit Hyperactivity Disorder (ADHD) or Attention Deficit Disorder (ADD), Down’s syndrome, cerebral palsy, muscular dystrophy, cystic fibrosis, sickle cell anemia, autism, diabetes, arthritis, congenital and other heart disease, asthma, allergies, colitis, anemia, ear infections, seizures, headaches, stuttering, and stammering. A question about whether the sample child still has asthma is included. This section also contains a question used to determine the number of school-loss days reported during the 12 months prior to the interview. In addition, respondents were asked about hearing and vision loss; if a health problem requires the sample child to use special equipment such as a brace, wheelchair, or hearing aid; whether the sample child’s health is better, worse, or the same compared with 12 months ago; and whether t he sample child currently has a problem that has required prescription medication for at least 3 months. Lastly, there are questions about the sample child’s height and weight.
In 1994 and 1995, the NHIS included a special supplement on disabilities designed to collect more extensive information on the disabilities and their effects.
Surveys Reporting Disability Information in a Non-Health Context
The other surveys discussed in this paper view a disability as an important demographic characteristic that may affect or be related to other information being collected by the survey. For example, disability status may have an effect on the extent and type of remodeling carried out by homeowners (data collected by the AHS) or on participation in the labor force (data collected by the CPS). The collection of information on disabilities is not the primary focus in any of these other surveys.
The long form of the 2000 decennial census contained six questions on disabilities. These questions, with modifications, are included in the American Community Survey. The AHS, CPS, and SIPP adopted these questions with appropriate modifications. Figure 1 contains the relevant questions from the 2011 ACS questionnaire.
In the context of the WHO model, questions 17a and 17b inquire about specific impediments: difficulty in hearing or seeing. These questions are asked of all persons. Questions 18a, 18b, and 18c inquire about the ability to perform specific activities, such as concentrating or decisionmaking, walking up stairs, and bathing and dressing. Questions 18a and 18b involve activities that are mostly one-dimensional (cognition and ambulation), whereas Question 18c involves activities that require both mental and physical abilities (bathing and dressing). These questions are asked of persons 5 years old or older. Question 19 inquires about the ability to 4
Figure 1: ACS Questions on Disabilities
5
perform functions outside of the home, such as doing errands or visiting a doctor; these functions also require both mental and physical abilities. Question 19 is asked of persons 15 years of age or older. The ACS questions represent an effort to collect information in an efficient manner (only six questions) on specific impediments and their effects on living in the home and outside of the home.
The AHS, CPS, and SIPP adopted versions of the ACS questions for four reasons: the six questions were very carefully designed, reviewed, and tested;6 they cover the most important disability characteristics; they impose minimal burden on respondents; and the consistency in questionnaire design makes it easier to combine information from multiple sources on how disabilities affect other economic and demographic variables.
Because of its labor market focus, the CPS contains a seventh question that focuses on the relationship between disability and participation in the labor force:
Do you have a disability that prevents you from accepting any kind of work during the next six months?
The long form of the 2000 decennial census included a similar question, but survey design and enumerator issues invalidated this measurement for Census 2000.7 Similar questions were included in the 2005 and 2006 ACS questionnaires but were omitted after 2006.
SIPP is a panel survey in which the same households are interviewed in successive waves. The SIPP “questionnaire” consists of a set of core questions that are asked in each wave and a series of topical modules that are asked as part of specific waves. The mix of topical modules changes with each SIPP panel, and not all modules are asked of each panel. The six questions are generally included in one of the topical modules. In addition, past SIPPs have had a topical module that explores in greater detail the relationship between disabilities and employment. The module looks at how health conditions limit the ability to work. The module asks about 29
specific health conditions, including hearing and vision problems, AIDS, cancer, and loss of limbs. An “other” category forms the 30th question in this sequence.
All the surveys ask the six questions at the person level. The AHS and ACS follow the same age structure in asking the questions: all persons are queried about problems with hearing and vision; persons 5 years old or older are queried about problems with cognition, walking, and bathing and dressing; and persons 15 years old or older are asked about problems with errands. The CPS and SIPP ask the disability questions only of persons 15 years old or older.
An important distinction is how the surveys report the information. The AHS reports information on disabilities at both the person and the household level. The ACS, CPS, and SIPP report information on disabilities only at the person level.
6 See Brault, Matthew W. 2009. Review of Changes to the Measurement of Disability in the 2008 American Community Survey. Washington, DC: U.S. Census Bureau.
7 The long form of the 1990 decennial census included a similar question about the relationship between disability and employment. The only other questions about disability in the 1990 long form dealt with the effects of disabilities on the ability to bathe or dress and the ability to run errands outside the home.
6
Choosing Among the Surveys
Two broad guidelines are obvious:
Researchers interested in how various health conditions create impediments that restrict the ability of individuals to perform certain functions or participate in various activities should use the NHIS because this survey contains very detailed information on the causes and consequences of disabilities.
Researchers interested in how disabilities affect specific variables should choose the survey that focuses on those variables. CPS or SIPP are the obvious choices for research into the effects of disabilities on employment, and the AHS is the obvious choice for research into the effects of disabilities on housing needs and choices.
Starting from these simple guidelines, we will now compare using the disability information in the AHS to using that in other surveys under specific conditions.
AHS and Person-Level Information on Disabilities
Compared to the ACS, the AHS suffers from several disadvantages for person-level analysis.
The major disadvantage is the absence of person-level weights. For the AHS, the Census Bureau provides only housing unit weights (PWT, WGT90GEO, or WEIGHT), while the ACS provides both person-level weights (PWGTP) and housing unit weights (WGTP).8 Table 1 compares population counts using the AHS and the ACS; the counts are for persons not living in group homes. The ACS count in the bottom line of the Table is derived by multiplying the number of persons in a household by the weighted number of households with that number of persons. The AHS and the ACS provide very similar population counts when the ACS uses housing unit weights just like the AHS does. However, when the ACS uses population weights, its estimate of the population is much closer to the official Census estimate.
Table 1: 2009 Population Counts from the AHS and ACS
Source
Number of persons in housing units
American Housing Survey
283.1 million
American Community Survey (person weights)
298.7 million
American Community Survey (housing weights)
285.6 million
Another unique advantage of the ACS is the provision of information on disabilities for persons living in group quarters. The ACS disability counts provided by the Census Bureau online through American Fact Finder are based on the civilian non-institutional population, which includes persons living in households and persons living in non-institut ional group quarters, a group totaling 301.5 million persons in 2009. One can obtain counts for persons living in 8 The capitalized expressions are variable names from the AHS and ACS public use files, respectively. The AHS has three weights, a pure weight (PWT), a weight based on 1980 geography (WEIGHT), and a weight based on 1990
geography (WGT90GEO).
7
households only, for persons living in group quarters, and for all persons by using the ACS
public use file (PUF).
Appendix A shows that the AHS and the ACS produce different estimates of the proportion of persons with specific disabilities. The ACS estimates are conceptually better because they use population weights, whereas the AHS estimates use housing weights. The estimates differ for other reasons. The AHS reports refusals and “don’t know” responses, but the Census Bureau imputes answers when ACS encounters refusals or “don’t know” responses. American Fact Finder indicates that 7 to 10 million of the 301 million in the 2009 ACS-tabulated responses were imputed. Finally, there are important data collection differences between the AHS and the ACS. The AHS relies mainly on telephone interviewing, while the ACS relies mainly on mail questionnaires. The length of the questionnaire and the sequences of questions also differ between the two surveys.
AHS and Household-Level Information of Disabilities
The AHS is the only survey among those discussed above that tabulates the person data at the household level and that provides household-level variables in its PUF. Household-level tabulations can be produced from the PUFs of the other surveys; however, most researchers would only consider the ACS as an alternative to the AHS for household-level information because the CPS and SIPP ask the disability question only of persons 15 years old or older. The NHIS can also be used to produce household estimates, but its greater detail on disabilities and health issues makes it more difficult to use.
The choice between the AHS and the ACS depends upon the goals of the research, as each survey has it strengths and weaknesses.
AHS strengths include:
• Household-level variables already exist.
• Survey collects more detailed information on both housing unit and household characteristics.
• Data collection by telephone interviews allows for more probing and interaction with respondents during editing.
• No imputations for refusals or “don’t know” responses – for users who prefer no imputations.
ACS strengths include:
• Much larger sample size allows analysis at the state and metropolitan area levels.
• Imputations for refusals or “don’t know” responses – for users who prefer imputations.
The next section compares household-level tabulations from the AHS and the ACS for 2009.
8
Disabilities at the Household Level: AHS vs. ACS
Before comparing the two surveys, a brief discussion is required about the differences between the AHS and the ACS in reporting the basic housing counts. Table 2 compares the counts from the two surveys of the housing stock, occupied housing units, and vacant units for 2009. By definition, the number of occupied housing units equals the number of households. The two key differences between the surveys involve the treatment of seasonal units and how vacancies are estimated. The AHS divides the housing stock into seasonal and year-round units and then divides year-round units into occupied and vacant units. The ACS classifies units occupied less than 2 months as vacant units if all the occupants have other residences. Among the types of vacant units recorded by the ACS are units that are “for seasonal, recreational, or occasional use.” In 2009, this group numb ered 4,706,000, which was approximately equal to the number of seasonal units reported by the AHS. If we adjust the AHS count of vacant units to include seasonal units, the AHS counts roughly 2 million more vacant units than the ACS. The ACS has a known bias in estimating vacancy. The ACS provides this guidance on vacancy: “The data on vacancy status were obtained only for a sample of cases in the computer-assisted personal interview (known as “CAPI”) follow-up by field representatives. Data on vacancy status were obtained at the time of the personal visit.” Vacant units had 2 months to become occupied before the ACS conducted a field interview; therefore, ACS vacancy rates should be lower than AHS
vacancy rates. Because both surveys use roughly the same count of the housing stock, the underestimation of vacancies by ACS results in an overestimate of occupied housing units or
households.9
Table 2: Differences in Housing Counts, AHS vs. ACS10
AHS ACS
AHS-ACS
Housing Stock
130,112,000
129,950,000
162,000
Year-round 125,494,000
NA
Occupied
(households) 111,806,000
113,616,000
-1,810,000
Vacant 13,688,000
16,334,000
-2,646,000
Seasonal 4,618,000
NA
Vacant + seasonal
18,306,000
16,334,000
1,972,000
Table 3 compares the incidence of various disabilities among households in 2009 using data from the PUFs from the 2009 AHS and the 2009 ACS. The Census Bureau collects information on disabilities at the person level; it puts variables that indicated whether a household has a member with a specific disability on the AHS PUF but not on the ACS public use microdata sample (PUMS). To produce the ACS portion of Table 3, we merged the housing and person ACS PUMS files and created variables that reproduce the information found on the AHS PUF.
9 This issue is discussed in greater detail in Comparison of Housing Information from the American Housing Survey and the American Community Survey by Frederick Eggers, a report prepared by Econometrica, Inc., for HUD in 2007. See pages 12-14. Found under technical supplements at
http://www.huduser.org/portal/datasets/ahs/ahsprev.html.
10 The counts in Table 2 come from American Housing Survey for the United States: 2009, Table 1-1, and from Tables B25002 and B25004 for the 2009 ACS on American Fact Finder.
9
Table 3: Comparison of Household Level Information on Disabilities: 2009 AHS vs. ACS
AHS ACS
Refused or
Type of disability*
With
All who
Maximum
With
Don't
Percent
All Percent
disability
responded
percent
disability
Know
Hearing
6,077,000
110,927,000
877,000
5.5% 6.2% 9,124,000
113,620,000
8.0%
Seeing 2,993,000
110,893,000
917,000
2.7% 3.5% 5,502,000
113,620,000
4.8%
Memory & related
5,817,000
110,847,000 956,000
5.2% 6.1% 10,474,000 113,620,000
9.2%
Walking 11,651,000
110,895,000
911,000
10.5% 11.2% 16,137,000 113,620,000
14.2%
Care 2,969,000
110,899,000
907,000
2.7%
3.5%
6,024,000
113,620,000
5.3%
Errands 6,206,000
110,996,000
813,000
5.6% 6.3% 10,642,000