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J Health Econ. 2017 May;53:72-86. doi: 10.1016/j.jhealeco.2017.02.004. Epub 2017 Mar 6.

Premium subsidies, the mandate, and Medicaid expansion: Coverage effects of the Affordable Care Act.

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Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Kresge 4th Floor, Boston, MA 02115, United States. Electronic address:
Massachusetts Institute of Technology and National Bureau of Economic Research, Department of Economics, E52-434, 77 Massachusetts Avenue, Cambridge, MA 02139, United States. Electronic address:
Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Kresge Room 406, Boston, MA 02115, United States. Electronic address:


Using premium subsidies for private coverage, an individual mandate, and Medicaid expansion, the Affordable Care Act (ACA) has increased insurance coverage. We provide the first comprehensive assessment of these provisions' effects, using the 2012-2015 American Community Survey and a triple-difference estimation strategy that exploits variation by income, geography, and time. Overall, our model explains 60% of the coverage gains in 2014-2015. We find that coverage was moderately responsive to price subsidies, with larger gains in state-based insurance exchanges than the federal exchange. The individual mandate's exemptions and penalties had little impact on coverage rates. The law increased Medicaid among individuals gaining eligibility under the ACA and among previously-eligible populations ("woodwork effect") even in non-expansion states, with no resulting reductions in private insurance. Overall, exchange premium subsidies produced 40% of the coverage gains explained by our ACA policy measures, and Medicaid the other 60%, of which 1/2 occurred among previously-eligible individuals.


Health insurance; Individual mandate; Medicaid; Tax credits

[Indexed for MEDLINE]

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