Physicians on board: An examination of physician financial interests in ASCs using longitudinal data

This paper investigates physician financial interests in ambulatory surgery centers (ASCs) using novel, longitudinal data that identify board members (directors) of ASCs in Florida. Improving on prior research, the estimated models in this paper disentangle physician director selection effects from the causal impact of these financial interests. The data suggest that even prior to their financial interest, physician directors had larger procedure volumes than non-directors. Physician directors also referred more lower-risk patients. On average, ASC board membership led to a 27% increase in a physician's procedure volume and a 16% increase in a physician's colonoscopy volume. Simulations suggest that 5% of the colonoscopies performed in Florida between 1997 and 2004 may have been due to physician ASC board membership. The evidence also suggests that physician directors steered patients from hospitals to their affiliate ASCs. In addition, they referred and/or treated more lower-risk patients as a result of board membership.