Health Returns to Access Expansion: Evidence on the Role of Delivery Capacity Across U.S. States

Although expansions in healthcare coverage and affordability are widely expected to improve population health, their effects on health outcomes are conditional rather than automatic. Improved access increases the opportunity for care use, but measurable health gains depend on whether delivery systems can provide timely and effective treatment and whether the outcomes under study are responsive to clinical intervention. Using a balanced panel of U.S. state–year data from 2006 to 2020, this study examines how healthcare access interacts with delivery capacity to shape cause-specific mortality. Effective access to care is measured as a multidimensional construct encompassing coverage, affordability, and connection to care, while delivery capacity is proxied by lagged healthcare workforce density. The results indicate that gains in access are associated with reductions in amenable mortality primarily in higher-capacity settings. In contrast, mortality outcomes less directly responsive to clinical care exhibit weaker or different patterns. Instrumental-variable estimates are consistent with these findings, although the instruments fall short of conventional strength thresholds and are interpreted using weak-instrument-robust methods. Overall, the findings suggest that the health returns to access expansion are conditional on delivery capacity: they are more likely to materialize where healthcare systems can translate formal access into timely and effective clinical care and where outcomes are within the reach of medical intervention.