matters of measurement issues to meet the Social Security Administration’s information needs, on the adequacy of the research design, and the implementation plan for the NSHA. The committee issued two interim reports (IOM, 1997a, 1999b) on its findings and conclusions based on its review. The first interim report provided a preliminary review of the general features of the proposed survey design, data collection plans, coverage, sampling plans, and operational decisions as described in the scope of work prepared by SSA in the draft request for proposals (RFP) for the conduct of NSHA. The committee believed that SSA needed to make important decisions about the survey design, the research and development work for the survey, and other basic features before issuing an RFP for the survey. It also discussed some of the limitations as they related to the efficiency of the sampling plan in terms of accepted statistical principles and practices. The committee’s third interim report reviewed and provided guidance on the sample design, instruments and procedures, and response rate goals for the pilot study. It also commented on the time line established by SSA for initiation of each phase of the survey. Both reports provided SSA with specific and detailed guidance on various aspects of the survey. SSA has responded by altering various features of the survey. All of the committee’s recommendations made in these reports can be found in Appendix C.


The National Study of Health and Activity is a complex, national sample survey designed to estimate the number and characteristics of a broad range of people with disabilities that affect their ability to work and carry out activities of daily living. SSA has contracted with Westat to conduct the survey. As originally conceived, the principal information goals of the NSHA were to

  1. Estimate the total number and characteristics of people who are severely enough impaired that, but for work or other reasons,1 they would meet SSA’s statutory definition of disability. (This group would represent the universe of potentially eligible nonbeneficiaries who could apply and meet the current criteria, but who are not now receiving benefits.)


The term work for SSA’s purposes refers to substantial gainful employment, which is generally about $780 per month for 2002. Other reasons for not receiving benefits include people who have chosen not to apply for disability, who have too many assets, who rely on family for support, or who are unaware of the program.

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