Did the Medicaid Expansion Harm the Medicare Population?

Abstract

While a large and growing literature has examined the effects of the Affordable Care Act (ACA) Medicaid expansion on newly eligible Medicaid recipients, relatively few studies have explored the impact of the expansion on the Medicare population. This study uses data on Medicare fee-for-service utilization and quality from 2007-2017 in conjunction with difference-in-difference models with a variety of inter-temporal controls and county fixed effects. It finds strong evidence of negative spillovers on the Medicare population. Beneficiaries in expansion states experienced reductions in their utilization of physician services (Evaluation and Management (E & M), procedures, and testing), increases in their use of hospital services (emergency room visits, outpatient visits, and inpatient care). Further, the quality of their care declined with reductions in the percentage of beneficiaries who had at least one primary care visit during the year, as well as reductions in the percentage of diabetic Medicare beneficiaries who had a recommended eye exam or LDL-C cholesterol screening.