Abstract for: Exploring Unintended Consequences of Physician Supply-oriented Policies: Insights from a Model of the Physician Workforce in the U.S.

Stakeholders increasingly expect physician workforce models that account for feedback, delays, and dynamic complexity rather than binary supply-demand comparisons. With persistent shortages affecting one-third of Americans across 8,504 health professional shortage areas, new modeling approaches are needed to support policy decisions addressing these shortages while representing the interconnected nature of healthcare workforce systems. We developed a system dynamics model for the Association of American Medical Colleges that represents the U.S. physician workforce as an integrated feedback system. The supply module simulates the complete training pipeline—from medical school through active practice—with explicit cross-flows between primary and specialty care pathways. We calibrated the model with 2002-2024 data and projected physician supply through 2052. Our model reveals counterintuitive consequences of supply-side policies: restricting specialty GME slots unexpectedly decreases primary care physician supply due to complex training pathway interactions; adding 14,000 residency slots increases physician supply, but continuing declines in average work hours largely offsets these gains; and changes to retirement age yield comparatively modest effects despite significant policy attention. These findings demonstrate how stock-flow structures and feedback loops generate system behaviors that conventional projection approaches cannot capture. The model highlights the critical distinction between centralized policy levers (GME slots) and aggregated individual choices (work hours, retirement), providing policymakers with a dynamic framework to develop multi-faceted approaches to physician shortage challenges. to assist in writing