Anecdotal evidence suggests that Social Security Disability Insurance (SSDI) beneficiaries intentionally restrain, or “park,” their earnings at a level below substantial gainful activity to retain cash benefits. But there is limited empirical evidence documenting such behavior. This article in Social Security Bulletin looks at the impact of the 1999 change in the substantial gainful activity earnings level on two cohorts of SSDI beneficiaries—one affected by the change and one not. The results show that, in a typical month from 2002 through 2006, between 0.2 and 0.4 percent of all SSDI beneficiaries were parked below the substantial gainful activity level in a typical month.