The NHIS, conducted by the National Center for Health Statistics (NCHS), is a principal source of information on the health of the civilian non-institutionalized population of the United States. Each year, the survey consists of a basic set of questions on health, socioeconomic and demographic items as well as one or more special questionnaires to obtain more detailed information on major current health issues. A Disability Follow-up special questionnaire was used in 1994-95. The NHIS also provides information about activity limitations and chronic conditions which are relevant to the topic of work and disability.

Survey of Income and Program Participation (SIPP)
The SIPP is a multipanel, longitudinal survey conducted by the U. S. Census Bureau. The data in this publication come from three SIPP files that are based on a number of overlapping waves and panels of the SIPP. On the SIPP, people age 15 and over were considered to have a disability if they met any the following criteria:

1. used a wheelchair or had used a cane or similar aid for 6 months or longer,
2. had difficulty performing a functional activity,
3. had difficulty with one or more activities of daily living,
4. had difficulty with one or more instrumental activities of daily living, or
5. were identified as having a developmental disability or a mental or emotional disability.

1. the person was 16 years and over and had a condition that made it difficult to do housework,
2. the person was between 16 and 67 years of age and had a condition that limited the amount or kind of work the person could do at a job,
3. the person was under 21 years of age and his or her parents responded on the survey about receipt of developmental services, and limitations in usual activities, the ability to do regular school work or the ability to walk, run, or use stairs, or
4. the person was under age 65 and covered by Medicare or received SSI.