In this appendix, information on the sources and limitations of the data is presented. The major surveys covered in this publication are the Current Population Survey (CPS), the National Health Interview Survey (NHIS), the Survey of Income and Program Participation (SIPP), the Annual Survey of Occupational Injuries and Illnesses (ASOII), and the Census. These surveys provide the most current national numbers and estimates from respondent-based information. Estimates from surveys are within the past 7 years.
The following summaries will cover the surveys, their sampling formats, the respondent size, and definitions of terms used in the surveys concerning work disability and how it is measured. More details can be found in the original publications.
NHIS - The National Health Interview Survey is a nationwide sample of households done by the National Center for Health Statistics (NCHS). It queries the civilian, noninstitutionalized population of the United States on its health. For disability purposes, it is concerned with activity limitations and chronic conditions.
Sampling - A multistage probability design permitting a continuous sampling of the civilian noninstitutionalized population living in the United States. Each weekly sample is representative of the target population and is additive with other weekly samples. Sampling is done throughout the year thus preventing seasonal bias. The samples are grouped in four major geographic regions: Northeast, Midwest, South, and West. Surveys after 1985 use a redesign of the sampling which reduces sampling units by half and oversamples the black population.
Respondents - The following samples were reached: 1993 - 109,671 persons and in 1994 - 116,179 persons. Response rate was approximately 95.6% in 1993 and 94.1% in 1994.
In 1990, the Assistive Devices Supplement was conducted. Of the nearly 120,000 persons interviewed in that year, 6,310 reported use of assistive devices, and 3,239 reported having home accessibility features. Sample cases were weighted to make the estimates of national statistics. Weights for each case adjust for several factors, including the nonresponse of some eligible households.
Definitions - Chronic condition is one noticed for three months or more, or being on the NCHS list of chronic conditions. Disability refers to any long or short-term reduction of a personžs activity as a result of an acute or chronic condition. Limitation of activity is a long-term reduction in a personžs capacity to perform the average kind or amount of activities associated with his or her age group.
SIPP - The Survey of Income and Program Participation is a longitudinal survey conducted by the Bureau of the Census. The data in this publication come from the third wave of the 1991 panel and the sixth wave of the 1990 panels of the SIPP. For the 1991-92 report, the topical modules included questions on disability status. The SIPP covers the noninstitutionalized population of residents living in the U.S.
Sampling - The same households are interviewed every four months. A cycle of four interviews covering the entire sample, using the same questionnaire, is called a wave. The 1990 panel contains an oversample of Black headed households, Hispanic headed households and female headed family households with no spouse present and living with relatives.
Respondents - The sample size for October 1991 to January 1992 was 34,000 households. While no numbers are given on number of individuals interviewed (because it is a household survey) , a rough estimate would be 85,000 (using an estimated 2.5 persons per household). The response rate ranged from 81.7% in October to 82.3% in November.
Definitions - Functional limitations are defined from the questions asked about the difficulty in performing basic functional activities (seeing, hearing, having one's speech understood, walking, carrying or lifting 10 lbs., and walking up a flight of stairs). A person age 15 and over was considered to have a Disability if they met the following criteria: (a) used a wheelchair; (b) had used a cane or similar aid for 6 months or longer; (c) had difficulty with a functional activity; (d) had difficulty with an ADL; (e) had difficulty with an IADL; or (f) was identified as having a developmental disability or a mental or emotional disability. A person also was considered to have a disability if: (g) the person were 16 years and over and had a condition that made it difficult to do housework; (h) the person were between 16 and 67 years old and had a condition that limited the amount or kind of work the person could do at a job; (i) the person were under 21 years old and their parents responded on the survey about receipt of developmental services, and limitations in usual activities, the ability to do regular schoolwork, or the ability to walk, run, or use stairs; and (j) the person were under age 65 and covered by Medicare or received SSI. Activities of daily living (ADLs) cover getting around inside the home, getting into and out of bed or a chair, bathing, dressing, eating, and toileting. Instrumental activities of daily living (IADLs) cover going outside the home, keeping track of money or bills, preparing meals, doing light housework, and using the telephone.
CPS - The Current Population Survey is a monthly survey done by the Bureau of the Census which deals mainly with labor force data for the civilian noninstitutional population. The part of the survey with which we are concerned for this publication is the March Income Supplement. Questions relating to labor force participation are asked of all members who are 14 or older in a household. In March, supplementary questions are asked about income thereby supplying the data for characteristics of noninstitutionalized persons with a work disability.
Sampling - The CPS sample was selected from the 1970 Census files covering all 50 states and the District of Columbia. The sample is continuously updated to reflect new construction.
Respondents - 60,500 households were eligible, but 2,500 were nonresponses (95.8% response rate). This translates into approximately 120,000 persons (assuming 2.5 people per household and lowering the estimate because the sample only includes ages 14 and above).
Definitions - Work disability is the only disability measured by the CPS. People are classified as having a work disability if they:
- have a health problem or disability which prevents them from working or limits the kind or amount of work they can do; or
- ever retired or left a job for health reasons; or
- did not work in the survey week because of long-term physical or mental illness or disability that prevents the performance of any kind of work; or
- did not work at all in previous year because of illness or disability; or
- are under 65 years of age and are covered by Medicare; or
- are under 65 years of age and a recipient of SSI (Supplemental Security Income); or
- received veteran's disability compensation.
ASOII - The Annual Survey of Occupational Injuries and Illnesses collects data on work-related injuries, illnesses, and fatalities for the Bureau of Labor Statistics from a random sample of private establishments.
Sampling - An independent sample is selected for each state. The sample design is based on the total recorded case incidence rate. The sample is stratified on the Standard Industrial Classification (SIC) code and employment.
Respondents - The survey covered 280,000 private establishments and represents about 83 million workers in the private sector.
ECA - The National Institute of Mental Health (NIMH) Epidemiologic Catchment Area Survey is a multisite epidemiologic and health services research study that assesses mental disorder prevalence, incidence, and service use rates. The five sites for the study and the participating universities which carried it out were New Haven, CT (Yale); Baltimore, MD (Johns Hopkins); St.Louis, MO (Washington University); Durham, NC (Duke); and Los Angeles, CA (UCLA).
Sampling - Population sizes in the five sites ranged from 270,000 to 420,000 with mixes of urban, rural, and suburban locations as well as ethnic and age compositions. One adult age 18 or over was surveyed in each of a probability sample of households in an area. Oversamples were done for elderly in New Haven and Durham, and blacks in St. Louis; and in Los Angeles, one area was predominantly Hispanics.
Respondents - A total of 18,571 persons were interviewed, ranging from 3,004 to 5,034 completed interviews at each site.
Definitions - The ECA diagnosed mental disorders according to the diagnostic criteria set forth in the Diagnostic and Statistical Manual of Mental Disorders - Third Edition (DSM-III) of the American Psychiatric Association.
NMES - The National Medical Expenditures Survey is a national probability sample of households done for the Agency for Health Care Policy and Research (AHCPR). It asked the civilian, noninstitutionalized population of the United States and medical providers about medical service use and expenditures, source of payments for health care, and health insurance coverage. It measured disability at two levels: activity limitations and activities of daily living (ADLs) limitations.
Sampling - The NMES has a stratified multistage area probability sample design . The survey oversamples for poor and low income families, the elderly, persons with functional limitations, blacks, and Hispanics. Participants were interviewed five times between February 1987 and July 1988.
Respondents - The screener interview occurred in 35,600 households. The resulting sample consists of approximately 35,00 persons in 14,000 households.
Definitions - Activity limitation is defined by age group. For those age 18 and over - if their health keeps them from working at a job, doing work around the house, or going to school; and being unable to do certain types of work, housework, or schoolwork because of health. For people age 5-17 - if the child attends or needs to attend special schools or classes because of an impairment or health problem; if the child is limited in school attendance or unable to attend school because of health; and if the child is limited in any way in any activities because of impairment or health. For children under age 5 - if the child was unable to take part in at all in the usual kind of play activities done by most children at this age; and if the child is limited in any way because of an impairment or health problem. Activities of daily living (ADLs) cover getting around inside the home, getting into and out of bed or a chair, bathing, dressing, eating, and toileting.