Antitrust Agencies May Not Be Able to Prevent High Concentration of Physicians in Many US Markets.

The growing concentration of physician markets throughout the United States raises antitrust concerns, yet government agencies have challenged only a few transactions. We show that many physician markets are highly concentrated according to the federal merger guidelines. But we also show that large physician groups became so primarily through piecemeal acquisitions of small practices and by hiring new physicians, two strategies that are unlikely to attract antitrust scrutiny. We suggest modest changes to current enforcement policy but question whether antitrust agencies will be able to meaningfully improve competitiveness in physician markets.