How Common is "Parking" Among Social Security Disability Insurance (SSDI) Beneficiaries? Evidence from the 1999 Change in the Level of Substantial Gainful Activity (SGA)

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 examining how beneficiary earnings and months off the rolls for work responded to a 1999 change in the SGA level for non-blind beneficiaries from $500 to $700 per month. Specifically, our difference-in-difference analysis compares longitudinal data for two beneficiary cohorts with different incentives to park their earnings; one experienced the increased SGA level the first year after its Trial Work Period (TWP), when beneficiaries can earn any amount without losing benefits, while the two-year-earlier cohort did not. The impact of the increased SGA level is consistent with parking, but its magnitude small. The reduction in TWP completers with earnings less than $500 was 1.0 percentage points, the reduction in the percentage with earnings over $700 was 1.2 percentage points, and the increase for those with earnings between $500 and $700 was 2.2 percentage points. However, there was no change in mean earnings; small increases for those with relatively low earnings were offset by reductions for those with relatively high earnings. The SGA increase had a significant negative effect on the average number of months that beneficiaries were off the rolls for work; the effect was largest -- about six-tenths of a month -- for those who earned $500 to $700 during in year they completed their TWP.