Who Enrolls in Coverage and Who Remains Uninsured? Medicaid Take‐Up Before and After the Affordable Care Act and During Unwinding

Policy Points The Affordable Care Act (ACA) dramatically expanded Medicaid eligibility in participating states. However, many eligible individuals remain uninsured because they do not enroll in (or "take up") coverage. The unwinding of the pandemic continuous enrollment provision in 2023-2024 further raised the importance of this issue. After the ACA, we found a significant increase in Medicaid take-up among eligible individuals across all eligibility pathways; these gains persisted into 2023, which coincided with the beginning of the unwinding. However, important vulnerabilities in enrollment are still apparent, including a steep drop-off in take-up when children become young adults and persistent lower take-up among childless adults and residents of nonexpansion states. These findings can guide policies in the postpandemic post-ACA era and suggest that efforts to reduce outreach or scale back the ACA will threaten coverage for many Medicaid beneficiaries. CONTEXT: Many uninsured individuals in the United States are eligible for Medicaid but not enrolled. The Affordable Care Act (ACA) expanded Medicaid eligibility starting in 2014, streamlined enrollment, and boosted outreach. During the 2020 COVID-19 pandemic, states were required to provide continuous coverage to Medicaid enrollees, a policy that ended in April 2023, with resulting coverage losses during the "unwinding" of this policy. METHODS: Using household data from the American Community Survey and state-level eligibility criteria, we assessed Medicaid participation among US citizens younger than 65 years old who either had Medicaid coverage or no insurance. We compared results before the ACA (2008-2010), after the ACA (2017-2019), and during "unwinding" (2023). We utilized logistic regression to identify predictors of take-up in each of these time periods. FINDINGS: The national take-up rate among Medicaid-eligible individuals rose from 76.5% before the ACA to 85.0% after the ACA. These gains persisted in 2023 as unwinding began, when take-up was slightly higher (86.5%) than before the pandemic. Post-ACA participation was highest among eligible children; Asian American, Pacific Islander, and Native Hawaiian and Black individuals; and residents of expansion states. Participation was lowest among adults ages 19-21 years old, American Indian and Alaska Native (AI/AN) individuals, employed adults, and those facing premiums for Medicaid coverage. Take-up improved post-ACA in both more and less deprived neighborhoods, whereas urban areas saw greater growth in take-up than rural areas. CONCLUSIONS: From the pre- to post-ACA period, Medicaid take-up rates among eligible individuals increased, and these gains persisted during the beginning of the unwinding period, potentially reflecting increased outreach efforts under the Biden administration. However, areas of vulnerability remain among young adults, working adults, AI/AN individuals, and those in rural areas. These findings have important implications as the unwinding period ends, and large changes to Medicaid may be considered after the 2024 elections.