Managed care, market power, and monopsony.

OBJECTIVE: To examine the theoretical possibility of monopsony behavior under managed care insurance. STUDY
DESIGN: Use of microeconomic theory to examine how managed care plans with market power would be expected to behave, and effects of that behavior on consumer and supplier welfare. PRINCIPAL
FINDINGS: The article shows that, under managed care monopsony, the welfare of consumers may be increased but overall economic welfare will necessarily be reduced. It offers a test for whether the lower prices paid by managed care buyers with larger market share represent welfare-reducing monopsony or a welfare-increasing movement away from provider monopoly. The test says that, if the quantity of inputs (supplied under conditions of increasing long-run marginal cost) declines, monopsony is present. The article also argues that the translation of lower provider prices into lower premiums is consistent with welfare-reducing monopsony by nonprofit health plans. In contrast, for-profit health plans that obtain monopsony may reduce the welfare of consumers as well as that of input suppliers. These theoretical conclusions are shown to be consistent with recent empirical research indicating a negative relationship between buyer market power and cost per enrollee.
CONCLUSIONS: Traditional antitrust policy has not been able to deal well with monopsony. The article concludes that health plans that use their market power to reduce medical spending may harm the well-being both of specialized medical workers and of consumers of medical care. Antitrust policy may need to be modified to deal with this situation.