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

Objective To examine the impact of the Affordable Care Act's coverage expansion on safety‐net hospitals ( SNH s). 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 SNH s and non‐ SNH s. Data Collection Methods 2013–2014 Healthcare Cost and Utilization Project State Inpatient Databases. Principal Findings On average per quarter postexpansion, SNH s and non‐ SNH s experienced similar relative decreases in uninsured stays ( DID  = –2.2 percent, p  =   .916). Non‐ SNH s experienced a greater percentage increase in Medicaid stays than did SNH s ( DID  = 13.8 percent, p  =   .041). For SNH s, the average decrease in uninsured stays (–146) was similar to the increase in Medicaid stays (153); privately insured stays were stable. For non‐ SNH s, the decrease in uninsured (–63) plus privately insured (–33) stays was similar to the increase in Medicaid stays (105). SNH s and non‐ SNH s experienced a similar absolute increase in Medicaid, uninsured, and privately insured stays combined ( DID  = –16, p  =   .162). Conclusions Postexpansion, non‐ SNH s experienced a greater percentage increase in Medicaid stays than did SNH s, which may reflect patients choosing non‐ SNH s over SNH s or a crowd‐out of private insurance. More research is needed to understand these trends.