RESUMEN
Fewer Social Security Disability Insurance (DI) beneficiaries have their earnings suspended or terminated because of work than those who are actually working, partly because beneficiaries "park" earnings at a level below substantial gainful activity (SGA) to retain benefits. We assess the extent of parking by exploiting the 1999 change in the SGA earnings level from $500 to $700 monthly for nonblind beneficiaries using a difference-indifference analysis that compares two annual cohorts of beneficiaries who completed their trial work period, one that was affected by the SGA change and one that was not. Our impact estimates, along with results from other sources, suggest that from 0.2 to 0.4 percent of all DI beneficiaries were parked below the SGA level in the typical month from 2002 through 2006. The SGA change did not yield any difference in mean earnings, although it did result in a small reduction in months spent off of the rolls because of work.