Research and Analysis by Jianting Hu
Counting the Disabled: Using Survey Self-Reports to Estimate Medical Eligibility for Social Security's Disability Programs
This paper develops an approach for tracking medical eligibility for the Social Security Administration's (SSA's) disability programs on the basis of self-reports from an ongoing survey. Using a structural model of the disability determination process estimated on a sample of applicants, we make out-of-sample predictions of eligibility for nonbeneficiaries in the general population. This work is based on the 1990 panel of the Survey of Income and Program Participation. We use alternative methods of estimating the number of people who would be found eligible if they applied, considering the effects of sample selection adjustments, sample restrictions, and several methods of estimating eligibility/ineligibility from a set of continuous probabilities. The estimates cover a wide range, suggesting the importance of addressing methodological issues. In terms of classification rates for applicants, our preferred measure outperforms the conventional single variable model based on the "prevented" measure.
Under our preferred estimate, 4.4 million people—2.9 percent of the nonbeneficiary population aged 18–64—would meet SSA's medical criteria for disability. Of that group, about one-third have average earnings above the substantial gainful activity limit. Those we classify as medically eligible are similar to allowed applicants in terms of standard measures of activity limitations.
We estimate a multistage sequential logit model reflecting the structure of the disability determination process of the Social Security Administration (SSA), as implemented by state Disability Determination Services (DDS) agencies. The model is estimated using household survey information exactly matched to SSA records on disability adjudications from 1989 to 1993. Information on health, activity limitations, demographic traits, and work is taken from the 1990 Survey of Income and Program Participation. We also use information on occupational characteristics from the Directory of Occupational Titles, DDS workload pressure, and local area economic conditions from unpublished SSA sources. Under the program provisions, different criteria dictate the outcomes at different steps of the determination process. We find that without the multistage structural approach, the effects of many of the important health, disability, and vocational factors are not readily discernible. As a result, the split-sample predictions of overall allowance rates from the sequential model performed considerably better than the conventional approach based on a simple allowed/denied logit regression.