LAUSR

The U.S. health care system is undergoing significant changes. Two prominent shifts include millions added to Medicaid and greater integration and consolidation among firms. We empirically assess if these two industry trends may have implications for each other. Using experimentally derived ("secret shopper") data on primary care physicians' real-world behavior, we observe their willingness to accept new privately insured and Medicaid patients across 10 states. We combine this measure of patient acceptance with detailed information on physician and commercial insurer market structure and show that insurer and provider concentration are each positively associated with relative improvements in appointment availability for Medicaid patients. The former is consistent with a smaller price discrepancy between commercial and Medicaid patients and suggests a beneficial spillover from greater insurer market power. The findings for physician concentration do not align with a simple price bargaining explanation but do appear driven by physician firms that are not vertically integrated with a health system. These same firms also tend to rely more on nonphysician clinical staff.