Effects of Medicaid Expansions 2001–2015 on Supplemental Security Income Program Participation Among Childless Adults

Growing research indicates that Medicaid expansions reduce Supplemental Security Income (SSI) participation, although the magnitude of effects may vary with the presence of other health policy reforms. We examine how a series of Medicaid expansions for childless adults before and after implementation of the Patient Protection and Affordable Care Act (ACA) impact SSI participation among childless adults. We use the Medical Expenditure Panel Survey to compare the change in SSI participation in states that expanded Medicaid coverage relative to those that did not during two time periods: 2001–2013 and 2001–2015. On average, SSI participation declined by a nonstatistically significant 0.10 percentage points (95% confidence interval [CI] = [−0.54, 0.32]) from a baseline SSI participation rate of 2.2% following Medicaid expansions implemented between 2001 and 2015. When restricted to the pre-ACA era, SSI participation declined by a nonstatistically significant 0.30 percentage points (95% CI = [−0.77, 0.16]). Although the direction of the point estimates suggests that Medicaid expansions before and after implementation of the ACA may be associated with reduced SSI participation, the imprecision of the estimates due in part to the sample size precludes this conclusion. To guide states in decision-making, it is essential to understand how increased Medicaid availability impacts SSI participation under different policy environments.