Building on the Evidence Base: Studies on the Effects of Medicaid Expansion, February 2020 to March 2021

The new financial incentive for expansion in the American Rescue Plan Act (ARPA) of 2021 has reignited debate on Medicaid expansion under the Affordable Care Act (ACA) in the twelve states that have not adopted the expansion. Further, the coronavirus pandemic has adversely affected health outcomes (as evidenced by suppressed health care utilization and increased excess mortality) and economic wellbeing. While Medicaid has served as a coverage safety net during the pandemic and resulting economic crisis, coverage options for many low-income adults are limited in non-expansion states.

This literature review provides context for these expansion debates by summarizing evidence from nearly 200 studies published between February 2020 and March 2021 on the impact of state Medicaid expansions under the ACA. This review builds on an earlier report (examining over 400 studies) concluding that expansion is linked to gains in coverage; improvements in access, financial security, and some measures of health status/outcomes; and economic benefits for states and providers (see Appendix A for figures summarizing study findings from the combined 601 studies from both reviews).

This recent body of research finds positive effects of expansion across a range of increasingly complex and specific categories. Accordingly, this report highlights study findings across multiple key themes of interest:

Studies included in this review may include multiple findings across multiple categories. Additionally, this report does not attempt to summarize all findings across all studies but instead aims to highlight conclusions across themes. A small number of studies reviewed and included in the appendices to this review did not have findings that fall into the thematic categories and thus are not cited in the text of this report.

This literature review summarizes findings from 197 studies of the impact of state Medicaid expansions under the ACA published between February 2020 and March 2021. This report builds on an earlier literature review that includes studies on the impact of expansion published between January 2014 (when the coverage provisions of the ACA went into effect) and January 2020. While the figures in this report (Appendix A) include the full body of 601 studies published between January 2014 and March 2021, the text of this report focuses on the 197 recent studies. Because this report highlights key themes across recent studies (versus attempts to summarize all findings in all studies), some recent studies included in the figures, bibliography, and appendices may not be cited in the text of this report.

This literature review includes studies, analyses, and reports published by government, research, and policy organizations using data from 2014 or later and only includes studies that examine impacts of the Medicaid expansion in expansion states. This review excludes studies on impacts of ACA coverage expansions generally (not specific to Medicaid expansion alone), studies investigating potential effects of expansion in states that have not (or had not, at the time of the study) expanded Medicaid, and reports from advocacy organizations and media sources.

To collect relevant studies, we conducted keyword searches of PubMed and other academic health/social policy search engines as well as websites of government, research, and policy organizations that publish health policy-related research. We also used a snowballing technique of pulling additional studies from reference lists in previously pulled papers. While we tried to be as comprehensive as possible in our inclusion of studies and findings that meet our criteria, it is possible that we missed some relevant studies or findings. For each study, we read the final paper/report and summarized the population studied, data and methods used, and findings. In instances of conflicting findings within a study, or if a reviewer had questions about specific findings, multiple reviewers read and classified the study to characterize its findings. In the report text, findings are broken out by key areas of interest, and studies may be cited in multiple of these categories or in multiple places within a category.


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