The Affordable Care Act (ACA) authorized the largest expansion of public health insurance in the U.S. since the mid-1960s. We exploit ACA-induced changes in the discontinuity in coverage at age 65 using a regression discontinuity based design to examine effects of the expansion on health insurance coverage, hospital use, and patient health. We then link these changes to effects on hospital finances. We show that a substantial share of the federally-funded Medicaid expansion substituted for existing locally-funded safety net programs. Despite this offset, the expansion produced a substantial increase in hospital revenue and profitability, with larger gains for government hospitals. On the benefits side, we do not detect significant improvements in patient health, although the expansion led to substantially greater hospital and emergency room use, and a reallocation of care from public to private and better-quality hospitals.
That is from a new NBER working paper by Mark Duggan, Atul Gupta, and Emilie Jackson.