Who Pays, Who Gains? ACA Medicaid Expansions and Changes in Net Income and Tax Liability by Socioeconomic Status

OBJECTIVE: To evaluate the effects of Affordable Care Act (ACA) Medicaid expansions on changes to net (after-tax) income and federal tax liability across socioeconomic status (SES). STUDY SETTING AND DESIGN: Event study and difference-in-difference analyses assessed the effects of state-level ACA Medicaid expansions post-2020 on net income and federal tax liability. DATA SOURCES AND ANALYTIC SAMPLE: Analyses were performed on nationally-representative survey data from the 2010 to 2023 Integrated Public Use Microdata Series Current Population Survey (IPUMS CPS) Annual Social and Economic Supplement (ASEC). We restricted the sample to individuals aged 18-65 with known information on sociodemographic characteristics. PRINCIPAL FINDINGS: Medicaid expansions contributed to overall net income growth (2.10%, 95% CI 1.31-2.89). By socioeconomic status, postexpansion net incomes were higher among individuals in the lowest income quintile (3.56%, 1.47-5.65), among those employed in low (4.90%, 2.74-7.07), low-mid (2.05%, 0.57-3.54), and mid-high (1.97%, 0.61-3.32) skill occupations, and among those with less than a high school degree (3.51%, 0.50-6.51), some college (3.39%, 1.47-5.32), or a bachelor's degree (1.94%, 0.32-3.56). Results further show an increase in overall federal tax liability after deductions (3.84%, 2.43-5.25), namely among individuals in the second (5.20%, 0.72-9.68) and third (4.58%, 2.31-6.86) income quintiles, among those in low (6.99%, 2.78-11.20), low-mid (6.82%, 4.05-9.60), and mid-high (2.71%, 0.42-5.01) skill occupations, and among those with a high school degree or GED (4.79%, 1.97-7.60) or a master's degree (7.99%, 3.70-12.28). CONCLUSIONS: Findings suggest ACA Medicaid expansions induced downstream net income gains while increasing overall federal tax revenue. Results further suggest that the increased costs of Medicaid expansion are not largely borne by higher SES groups. Broadly, Medicaid expansions may provide substantial economic benefits to the entire U.S.