This chapter, which addresses three categories of explanation—the characteristics of individuals insured by the Disability Insurance (DI) program, the state of the economy, and the generosity of program benefits—argues that the growth in DI rolls is likely to continue and perhaps accelerate going forward. The data indicate that the recessions of 1991 and 2001 can explain 24 percent of the growth in DI receipt among men and 12 percent of the growth among women. Changes in health during the past two decades have slowed rather than added to the growth of the DI rolls. DI awards for certain conditions were much more affected by the liberalized medical eligibility criteria than others. The aging of the Baby Boom population will result in significant increases in DI receipt during the next fifteen years. The incentive to apply for DI will increase with the rising value of health insurance through Medicare.