We study the role of physicians in driving geographic variation of US healthcare utilization. We estimate a model that … separates variation in average utilization of Medicare beneficiaries due to physicians, non-physician supply side factors, and … patient demand. The model is identified by migration of patients and physicians across areas, as well as by variation in …

. In these ways, AI may wither complement or substitute for physicians. We argue that AI represents the culmination of …

: the number of physicians in the physician's group (if any); the physician's integration with or employment by a hospital … or hospital system; and the average age of the other physicians in the physician's group. We present three key findings …. First, all else held constant, group physicians prescribe far fewer opioids, and prescribe them more appropriately, than do …