Over the past 20 years, the Supplemental Security Income Program (SSI), which provides federally funded income support for disabled individuals, has become one of the most important means‐tested cash aid programs in the United States. However, little research has examined the determinants of growth in SSI caseloads across states and over time. In this paper I use state panel data, exploiting variation both across states and over time, to determine what factors determine SSI disabled caseloads. I examine the relative importance of a number of factors, including economic conditions, health conditions, relative program generosity, and state fiscal situations. I then examine the effect of welfare reform as well as the effect of variation across states in welfare policies. Given previous research that provides evidence of interactions between the SSI program and other welfare programs that provide income support to single‐mother families, I also examine how the effects of the factors listed above have changed since the passage of major welfare reform in 1996. Results suggest that both economic conditions and welfare reform have significant effects on SSI participation and that the SSI program has become more responsive to business cycles since welfare reform.
JEL Classifications: J22, I38, I12, H53