Early Effects of the ACA Medicaid Expansion on Coverage, Access, Affordability and Health Outcomes for Low-Income Adults
We use changes in the Medicaid income eligibility threshold for both parents and childless adults within states over time to identify the effects of changes in eligibility for low-income adults (19-64). Using person-level data from the National Health Interview Survey (2010-2014), we measure insurance coverage, access to care, affordability of care and health outcomes for adults with incomes up to 138 percent of poverty. We estimate linear probability models on binary outcomes and include person and county-level controls as well as state and year fixed effects. We also estimate separate models for parents and childless adults.
Using the changes in the eligibility threshold to identify the effects of the Medicaid expansion has several advantages. It captures the variation in the magnitude of the expansion across states, but does not require the imputation of individual eligibility which is challenging due to measurement error in income and other eligibility criteria. Further, it provides a straightforward approach for simulating the effects of a change in the eligibility threshold, which we use to predict the effects of expanding Medicaid in the 25 states that had not expanded as of January 2014.
Preliminary results suggest that the expansion increased Medicaid coverage, decreased uninsurance and decreased private coverage, with magnitudes suggesting crowd out of employer coverage of approximately 30 percent. Moreover, we find that expanding eligibility increased ambulatory care visits, and reduced the share of low-income adults with an unmet need due to cost in the past year. Early impacts showed no improvement in general health status in response to expanded Medicaid eligibility, but some evidence of a reduction in severe psychological distress. We find significant benefits of eligibility expansion for both parents and childless adults, despite much smaller increases in eligibility for parents under the ACA. We are currently exploring the sensitivity of our results to varying our methods for measuring income as well as excluding noncitizens and/or specific states (e.g., California) from our sample. We are also considering a variety of falsification tests to further check the robustness of our results.
The magnitudes of some effects are small, but the results reflect relatively early progress under the ACA. Our results also confirm significant missed opportunities for low-income adults in states that did not expand Medicaid in 2014. These states generally have very low Medicaid eligibility thresholds for adults and would therefore see large eligibility increases if they chose to expand. As a result, the potential coverage, access and health status gains in nonexpansion states are larger than the observed gains in the states that actually expanded in 2014.