to 67 years also means that disabled workers may remain on the rolls for two additional years before converting to Social Security retirement. An improved understanding of the dynamics of the programs and the factors that influence them is required. At this time, little is known with certainty about what contributes to disability trends and to what degree. Ongoing and future research using new data sources, such as the data that will be generated by the National Study of Health and Activity and other SSA administrative files, should provide relevant information about disability program participation and cost and other related policy issues.

Moreover, as aptly stated by Burkhauser et al. (2001), “no studies have been able to satisfactorily disentangle the impact of demand side factors related to the passage of the ADA or changes in the mix of jobs in the economy in the 1990s from supply side factors related to changes in the ease of access to SSDI and SSI benefits or to a r oeduction in the share of jobs that provide private health insurance, which would discourage work among the population with disabilities.” Research is needed to delineate the magnitude of the various effects in order to understand the causes of recent declines in employment among people with disabilities. Only then can policies be developed to reverse the trend.