While the Medicaid expansion was intended to be national, the June 2012 Supreme Court ruling essentially made it optional for states. As of June 2018, 17 states had not expanded their programs.
Medicaid eligibility for adults in states that did not expand their programs is quite limited: the median income limit for parents in these states is just 43% of poverty, or an annual income of $8,935 a year for a family of three in 2018, and in nearly all states not expanding, childless adults remain ineligible. Further, because the ACA envisioned low-income people receiving coverage through Medicaid, it does not provide financial assistance to people below poverty for other coverage options. As a result, in states that do not expand Medicaid, many adults fall into a “coverage gap” of having incomes above Medicaid eligibility limits but below the lower limit for Marketplace premium tax credits (Figure 1).
This KFF brief presents estimates of the number of people in non-expansion states who could have been reached by Medicaid but instead fall into the coverage gap, describes who they are, and discusses the implications of them being left out of ACA coverage expansions. An overview of the methodology underlying the analysis can be found in the Methods box at the end of the report, and more detail is available in the Technical Appendices available here.