The Impact of Insurance Expansions on the Already Insured: The Affordable Care Act and Medicare†

Some states have not adopted the Affordable Care Act (ACA) Medicaid expansions due to concerns that the expansions may impair access to care and utilization for those who are already insured. We investigate such negative spillovers using a large panel of Medicare beneficiaries. Across many subgroups and outcomes, we find no evidence that the expansions reduced utilization among Medicare beneficiaries and can rule out all but very small changes in utilization or spending. These results indicate that the expansions in Medicaid did not impair access to care or utilization for the Medicare population.