One of the many supposed evils of the health care marketplace is the ambulatory surgery center (ASC), a facility which supposedly drains patients from traditional hospitals and constrains cross-subsidization of medical services. However, a new paper by Charles Courtemanche and Michael Plotzke in the Journal of Health Economics finds only very modest overlap between ASCs and surgery performed at traditional hospitals. The paper's abstract:

This paper estimates the effect of ambulatory surgical centers (ASCs) on hospital surgical volume using hospital and year fixed effects models with several robustness checks. We show that ASC entry only appears to influence a hospital's outpatient surgical volume if the facilities are within a few miles of each other. Even then, the average reduction in hospital volume is only 2–4%, which is not nearly large enough to offset the new procedures performed by an entering ASC. The effect is, however, stronger for large ASCs and the first ASCs to enter a market. Additionally, we find no evidence that entering ASCs reduce a hospital's inpatient surgical volume.

This finding is something to keep in mind when folks who restrain ASCs bleat about how their reforms expand access to health care.