Eligibility for and Enrollment in Medicaid Among Nonelderly Adults After Implementation of the Affordable Care Act.

The Affordable Care Act's (ACA) Medicaid expansion resulted in substantial gains in coverage. However, little research has documented eligibility or participation rates among eligible adults in the post-ACA period in part because of the complexities involved in assigning eligibility status. We used simulation modeling to examine Medicaid eligibility and participation during 2014 to 2017. More than one in five adults were Medicaid eligible in expansion states in the post-ACA period. In contrast, about one in 30 adults were Medicaid eligible in nonexpansion states. While eligibility rates differed substantially by expansion status, participation rates among Medicaid-eligible adults were similar in both sets of states (44% to 46%). These estimates indicate that differences in eligibility rather than in participation rates explained differences in enrollment between expansion and nonexpansion states during the study period. Participation in Medicaid is expected to grow during the coronavirus pandemic. Our study provides baseline estimates for future analyses of enrollment trends.