Identifying Associations Between State Medicaid Expansion Decisions and Spatial Disparities in County Insurance Rate Changes Under the Affordable Care Act

By the end of 2014, twenty-four states rejected Medicaid expansion, providing a unique opportunity to examine changes in insurance coverage rates after the implementation of the Affordable Care Act within and between states that did versus did not expand Medicaid. Using multilevel regression analyses of county-level non-elderly adult small area health insurance estimates (N = 3135) from the US Census Bureau, several important findings emerge. Compared to counties located in states that did not expand Medicaid, counties located in states that did expand experienced significantly larger increases in adult health insurance coverage rates between 2013 and 2014, net of the county baseline insurance coverage rate, socioeconomic and demographic composition, and labor market characteristics. In states that did not expand Medicaid, counties with larger shares of vulnerable residents (i.e., poor adults and low education) experienced lagging improvements in health insurance coverage. However, counties in states that expanded Medicaid were protected from several of these exacerbated disparities, and in some cases, experienced larger insurance coverage improvements than counties with less disadvantaged populations. These findings suggest that although insurance coverage increased in nearly all counties between 2013 and 2014, increases would have been larger and disparities would have been further alleviated if more states with highly concentrated vulnerable populations had expanded Medicaid.