Gaffney A, et al. – Via performing a repeated cross-sectional studies, investigators determined how implementation of Medicare and Medicaid (1966) and the Patient Protection and Affordable Care Act (2014) impacted hospital use. Participants included respondents to the National Health Interview Survey (1962-1970) and Medical Expenditure Panel Survey (2008-2015). In the 3 years prior to the implementation of Medicare and Medicaid and in the 4 years after, overall hospital discharges averaged 12.8 per 100 persons and 12.7 per 100 individuals, respectively. In the first 2 years following implementation, hospital days did not change but progressed later. Among the old, effects varied by subpopulation. That is, adjusted discharges grew by 2.4 per 100 persons in contrast to non-elderly persons, and also increased in those with low incomes vs high-income populations. Use declined for younger and higher-income individuals. In unadjusted (but not adjusted) analyses in persons reporting good or better health status, trends varied for some subgroups; in those in worse health, rates declined significantly and increased non-significantly. Hence, in society-wide hospital use, past coverage expansions were correlated with little or no variation, and increases in groups who gained coverage were offset by reductions among others, suggesting that bed supply restricted increases in use. Moreover, decreasing coverage may simply shift care toward wealthier and healthier individuals. Conversely, if growth in hospital capacity was carefully constrained, universal coverage was unlikely to lead to a surge in-hospital use.