American Community Survey (2003): Disabilities Nationwide

In a previous post, I took a quick look at how the total household population figure in the American Community Survey (ACS) for 2003 was calculated.  The numbers involved are not precise in every case, but the general concept appears to be that the "resident population" is divided into people who live in households and those who live in group quarters (e.g., prisons, hospitals, dormitories).  In the 2003 ACS, only households were examined.  The total number of people in the U.S. who were living in households in 2003 was estimated to be 282,909,885.  Of those, an estimated 176,395,446 fell into the traditionally defined working-age population aged 18-64.

The next thing to figure out, in moving toward statistics on disabilities at the county level, was how many of those 176,395,446 people were considered to have various kinds of disabilities.  Here, as before, I relied on the analysis of 2003 ACS data provided by Weathers (2005) in his Guide to Disability Statistics from the American Community Survey.  The previous post notes that the ACS understates disabilities when compared to some other national surveys; however, it has the advantage of being updated on the county level, and thus provides an essential stepping-stone in this investigation.

Weathers (2005) divides that total of 176,395,446 working-age people into those with (12%) and without (88%) disabilities, as defined by the ACS.  Weathers further narrows the working-age population down to the 25-61 age range, considering the 18-24 group as being of a "school-to-work transition age" and the 62-64 group as being of "early Social Security retirement age" (p. 19).  Since the 25-61 group accounts for 83% (i.e., 17,146,845) of the total of 20,609,733 people with disabilities in the larger 18-64 group (p. 54), I will tend to focus on that 25-61 group in this post.

To summarize, then, the ACS gives us, in 2003, an estimated 17,146,845 U.S. residents who lived in households (as distinct from group homes), had one or more disabilities, and fell into the 25-61 age group.  These people comprised roughly 10% of the estimated working-age (18-64) population of about 176 million.

According to Weathers (2005, p. 35), the ACS draws upon World Health Organization (WHO) concepts of impairment, activity limitation, and participation restriction, as expressed in the International Classification of Functioning, Disability and Health (ICF) (pp. 4-5).  In the ICF, Weathers says, an impairment is a significant deviation or loss in body function or structure (e.g., vision loss).  An activity limitation is difficulty in executing activities of daily living (e.g., dressing).  A participation restriction is a problem that a person may have in a life situation (e.g., lack of employer accommodation to the person's severe health condition).

As Weathers (2005, pp. 10-11, 35) describes, the ACS uses six questions to operationalize those ICF concepts.  Three of the six ask about impairments:  sensory, physical, or mental.  One asks about activity limitation, in the form of an inability to care for oneself inside one’s home.  Two ask about participation restrictions, in the form of physical, mental, or emotional conditions that prevent the person from going outside the home (e.g., to shop) or from working at a job or business.  The ACS defines disabilities as the presence of any one or more of these kinds of disability. As an example of how these questions may fail to count some disabilities, Weathers (p. 27) indicates that the question of going outside the home, used on the ACS, is narrower than the concept of Instrumental Activities of Daily Living (IADLs) used in some surveys.

The 2003 ACS data indicate that, for the 25-61 group, two of these six questions (pertaining to physical impairment and employment restriction) account for 55% of all disabilities.  Those two plus the next most frequently cited disability, regarding mental impairment, account for 70% of all disabilities in that age group.  Yet within that statement lies an interesting age-related permutation.  First, as one might expect, age is a factor in the calculation of disability under the ACS.  The data show that disability prevalence rates rise from 6.3 in the 5-17 group (that is, 6.3% of people in that age group have a disability) to 39.9 in the 65+ group (Weathers, 2005, p. 39).  At the same time, however, while those top three questions account for about 70% of disabilities in all three working age groups (i.e., 18-24, 25-61, and 62-64), the share due to mental impairments steadily declines.  Mental impairments constitute 30% of all disabilities in the 18-24 group, but only 15% in the 25-61 group and 10% in the 62-64 group.

It is not that mental impairments actually decline with age, though that may be the case for some kinds of mental impairments.  It is, rather, that mental impairments rise only slightly, from 3.7 in the 18-24 group to 5.8 in the 62-64 group.  This is quite different from the ninefold rise in physical disabilities between those two groups.  One explanation for that contrast is that the ACS may undercount mental disabilities in adults.  There is evidence of reduced awareness of mental disability on the part of adults and their primary care physicians (e.g., Surman, Wigal, & Lakes, 2009).  Undercounting of mental disabilities in adults would also be unsurprising if significant mental disabilities are incompletely conceptualized among adults (e.g., Nijmeijer et al., 2008, p. 701).

So far in this series of posts on statistics pertaining to disabilities, I have rarely gone beyond the relatively general descriptive approach provided by commentators such as Weathers (2005).  The preceding paragraph suggests, though, that a look at more critical or focused literature may highlight a number of shortcomings with the ACS, for purposes of counting disabilities.  As an example of another area in which a more refined approach may considerably enhance the statistical picture, one may review Weathers's remark (above) about the refinement that the IADL concept adds to the question of going outside the home.  Unless Weathers meant to contrast IADL against the ACS's question regarding self-care, and simply misspeaks on that point (compare pp. 27 and 39), it seems appropriate to question the finding that 6.9% of people in the 25-61 age group experience a significant employment restriction due to disability, and yet only 2.0% report a limitation in their self-care activity.  Without a boss or other reminder of a set goal, people at home may be more likely to adjust their goals and lives to accommodate their disabilities.

Those examples of potential shortcomings in the ACS may or may not be borne out in the professional literature.  I can't say; I haven't gotten that far yet.  The purpose of those remarks was simply to highlight a few ways in which the ACS may undercount disabilities.  Having achieved that, the next step in this investigation is to move from the national-level ACS data to the state level.

American Community Survey (2003): National Population Statistics

As described in a previous post, I found that the Cornell University Disability Statistics website offered materials that seemed likely to help me estimate the number of people with disabilities (PWDs) in a particular county in the U.S.  The next step was to understand something about the general population terminology and concepts that formed the basis for census calculations.

I had learned that the American Community Survey (ACS) provided the most frequently updated and most recent county-by-county data.  The Guide to Disability Statistics from the American Community Survey (Weathers, 2005, p. 28) indicates that estimates of the numbers of PWDs depend directly upon the number of questions asked. According to Weathers (p. 4), the ACS approach has several limitations:

First, the ACS is limited to six questions that are used to identify the disability
population [as a whole] and it does not allow one to identify the prevalence of specific health conditions (e.g., cancer, paralysis, HIV/AIDS, etc.). Second, the ACS definition does not explicitly include important societal and environmental factors that may contribute to a disability such as discrimination and lack of reasonable accommodations. Finally, the ACS does not capture the population living in “group quarters.” Group quarters include individuals living in institutions, college dormitories, and other types of group quarters. This is a very important limitation in that it may leave out an important segment of the population with disabilities. The Census Bureau plans to address this last limitation of the ACS by including a sample of persons living in group quarters beginning in 2006.

By contrast, at the low end of the scale, according to the Guide to Disability Statistics from the Current Population Survey - Annual Social and Economic Supplement (March CPS) (Burkhauser & Houtenville, 2006, p. 19), the Current Population Survey asks just one question about disabilities -- regarding, specifically, the presence or absence of a work limitation -- and thus "misses a large part of the broader population with disabilities based on an ICF [i.e., International Classification of Functioning] disability conceptualization."  On the other extreme, as Burkhauser & Houtenville (2006, p. 19) also note, the Survey of Income and Program Participation (SIPP) uses 93 disability-related questions.  Generally, they say, "data sets that ask more questions to identify a population with disabilities and that contain a broader disability conceptualization will capture a larger disability population."

Weathers (2005) quantifies the difference made by these varying operationalizations of the concept of disability.  Weathers uses data from 2003.  To analyze these data, it may be helpful to begin by clarifying the meanings of some terms that the Census Bureau uses.

First, the resident population of the U.S. includes all U.S. residents living in the 50 states and the District of Columbia.  That is, it excludes residents of Puerto Rico and American possessions abroad, as well as U.S. citizens living abroad, whether in the military or as expatriates.  This post does not examine the question of whether PWDs may be disproportionately represented in the military -- whether, that is, the percentages of PWDs in their home counties would be noticeably higher (particularly in some age groups and locations) if those members of the Armed Forces were available for inclusion within the count of PWDs under the ACS.

The resident U.S. population as of July 1, 2003 was estimated to be 290,210,914.  According to the 2003 ACS Subject Definitions (p. 13), the resident population is divided into people who live in housing units (i.e., households) and those who live in group quarters.  "Housing units" can include any occupied "unit," including tents and railroad cars; but "If all the people staying in the unit at the time of the interview are staying there for two months or less, the unit is considered to be temporarily occupied, and classified as 'vacant'" (p. 14).  The data include transients (i.e., those who stay only briefly in any one place), however, by including them if there is no place where they usually stay.  Note that "Vacant units are excluded from the housing inventory if they are open to the elements; that is, the roof, walls, windows, and/or doors no longer protect the interior from the elements. Also, excluded are vacant units with a sign that they are condemned or they are to be demolished" (p. 14).  It preliminarily appears, then, that the 2003 ACS data undercount people who are not living in any kind of housing unit but, rather, are living outdoors (e.g., under a bridge) -- among whom, again, there may be a disproportionate number of PWDs.

The Census Bureau indicates that residents of group quarters were sampled in 1999 and 2001, but the 2003 data exclude people living in group quarters.  For purposes of introducing some relevant terms, then, it will be convenient to refer to the 2000 census.  According to the Statistical Abstract of the United States for 2003, table 77 (examining 2000 census data), about 7.8 million people (2.8% of the total resident population of 281,424,602 in 2000) lived in group quarters.  These people were divided almost equally into institutionalized and noninstitutionalized group quarters.  Among the institutionalized individuals in group quarters, by far the largest groups were males aged 18-64 in correctional institutions (44%) and females aged 65+ in nursing homes (29%).  Other institutions include mental hospitals and wards and juvenile facilities.  Among noninstitutionalized individuals in group quarters, 55% were living in college dormitories.  Other noninstitutional group quarters include military quarters, religious group quarters, shelters, and group homes. 

If 2.8% of the total resident population lived in group quarters in 2003, as was the case in 2000 (above), that would mean that just over 8 million (i.e., 2.8% of 290,210,914) lived in group quarters in 2003.  Subtracting those 8 million from the total resident population would produce something like the 282,909,885 people whom the Census Bureau estimated as the total household population in 2003.

The total household population included people of all ages.  In the analysis of disabilities done by Weathers (2005), however, the focus is on people who were between 18 and 64 years of age in 2003.  In the 2003 ACS, to use the slightly adjusted number provided by Weathers, the Census Bureau estimates that there were 176,395,446 people in this age group.  This number is quite close to the 176,305,337 estimated by the SIPP for that year, and roughly midway between the estimates of 172,761,000 from the NHIS and 179,132,544 provided by the CPS.

I will be using the ACS figure in the next step, which addresses the numbers and percentages of people with disabilities within that larger total.  At this point, I join Weathers (2005) in turning from the estimate of the total numbers of people with disabilities in the population, and focus (at least for the time being) upon the prevalence of disabilities among people of traditional working (i.e., post-high school, pre-retirement) age.