Sources of Geographic Variation in Health Care: Evidence from Patient Migration

We study the drivers of geographic variation in US health care utilization, using an empirical strategy that exploits migration of Medicare patients to separate the role of demand and supply factors. Our approach allows us to account for demand differences driven by both observable and unobservable patient characteristics. We find that 40-50 percent of geographic variation in utilization is attributable to patient demand, with the remainder due to place-specific supply factors. Demand variation does not appear to result from differences in past experiences, and is explained to a significant degree by differences in patient health.