The Effect of Aca's Medicaid Expansion on Insurance Coverage Among Low Income Adults (WITHDRAWN)

Background/Purpose: Nearly 16.7 million additional individuals were enrolled in Medicaid and CHIP in January 2017 as compared to the period prior to the start of the first open enrollment period. Previous studies showed significant decreases in the uninsured rate among low income adults. However, most findings were based on changes in dependent coverage among young adults. Studies on nonelderly adults aged 19-64 focused on particular states to examine the effect of Medicaid expansion and observed a short period. This study had two specific aims: (1) assess national changes in insurance coverage during 2000 and 2016; and (2) analyze insurance coverage among low income nonelderly adults, comparing Medicaid expansion states and non-expansion states and Medicaid-eligible and -ineligible groups, for the pre-ACA period and post-ACA period.

Methods: Data came from seventeen waves of the March Annual Demographic File and Income Supplement of the U.S. Current Population Survey (CPS) (2000-2016). Our analytic sample was restricted to nondisabled adults between age 19 and 64 with household incomes below 200% of Federal Poverty Level. Further, we excluded people who were already eligible for Medicaid prior to the ACA so that we could define who became newly eligible for Medicaid (final sample size=198,380). We implemented difference-in-difference models with the adults with incomes below 138% of Federal Poverty Level living in expansion states as the treatment group and those with incomes above 138% as the control group. Three alternative comparison groups were used to test the sensitivity of the results: (1) adults with incomes below 138% in non-expansion states; (2) adults who are eligible for neither Medicaid or Marketplace subsidies in non-expansion states; and (3) adults who did not fall in coverage gap but had limited incomes to purchase insurance in Marketplace.  

Results: The ACA Medicaid expansions were associated with a significant increase in both Medicaid coverage and any type of insurance coverage, controlling for individuals’ sociodemographic characteristics and the year-to-year change in state-level characteristics (unemployment rates, per capita income, logged population size, democratic party, and minimum wage) that might have affected their insurance purchasing behavior. The net change after the ACA in both Medicaid and (any type of) insurance coverage in expansion states, as compared with control states, appeared to be significant. Sensitivity analyses with the additional comparison groups also yielded the significant effect of the ACA on insurance coverage.     

Conclusions and Implications: Benefits from observing such a long period allowed us to consider partial impact of economic recovery from Great Recession and early Medicaid expansion states. State Medicaid expansions were significantly associated with improved insurance coverage among low income adults. With the expected increases in insurance coverage resulting from the expansion, stakeholders may need to monitor local health care system capacity and respond where needed with policy- and/or market-based efforts as well as the low-income adults who still fall in coverage gap.