Trends in the characteristics of DI and SSI disability awardees and duration of program participation.

We analyze the effects of trends in the age and diagnostic mix of new disability awardee cohorts from 1975 through 1993 on expected duration on the Disability Insurance (DI) and Supplemental Security Income (SSI) rolls. The 1975-93 shift toward younger awardees is estimated to increase duration by 1.4 years for DI and about 5 years for SSI. Much of the increase in SSI duration is attributable to the recent influx of childhood awardees. For working age adults, the DI and SSI trends are comparable. We also estimate that about half of the 1975-93 increase in DI duration is explained by the increase in the proportion of younger DI-insured workers. During the 1993-2006 period, the effect of changes in the age mix of DI-insured workers will be reversed. This will moderate, but not eliminate, likely upward pressures on caseloads arising from the anticipated rise in incidence rates and the future effects of past increases in expected duration.