Early Impact of the Affordable Care Act Coverage Expansion on Safety-Net Hospital Inpatient Payer Mix and Market Shares

Published in: Health Services Research [Epub January 2018]. doi:10.1111/1475-6773.12812

Posted on RAND.org on February 14, 2018

by Vivian Y. Wu, Kathryn R. Fingar, H. Joanna Jiang, Raynard Washington, Andrew W. Mulcahy, Eli Cutler, Gary Pickens

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To examine the impact of the Affordable Care Act's coverage expansion on safety-net hospitals (SNHs).

Study Setting

Nine Medicaid expansion states.

Study Design

Differences-in-differences (DID) models compare payer-specific pre-post changes in inpatient stays of adults aged 19-64 years at SNHs and non-SNHs.

Data Collection Methods

2013–2014 Healthcare Cost and Utilization Project State Inpatient Databases.

Principal Findings

On average per quarter postexpansion, SNHs and non-SNHs experienced similar relative decreases in uninsured stays (DID = -2.2 percent, p = .916). Non-SNHs experienced a greater percentage increase in Medicaid stays than did SNHs (DID = 13.8 percent, p = .041). For SNHs, the average decrease in uninsured stays (-146) was similar to the increase in Medicaid stays (153); privately insured stays were stable. For non-SNHs, the decrease in uninsured (-63) plus privately insured (-33) stays was similar to the increase in Medicaid stays (105). SNHs and non-SNHs experienced a similar absolute increase in Medicaid, uninsured, and privately insured stays combined (DID = -16, p = .162).


Postexpansion, non-SNHs experienced a greater percentage increase in Medicaid stays than did SNHs, which may reflect patients choosing non-SNHs over SNHs or a crowd-out of private insurance. More research is needed to understand these trends.

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