In the constant attention paid to what drives health care costs, only recently has scrutiny been applied to the power that some health care providers, particularly dominant hospital systems, wield to negotiate higher payment rates from insurers. Interviews in twelve US communities indicated that so-called must-have hospital systems and large physician groups--providers that health plans must include in their networks so that they are attractive to employers and consumers--can exert considerable market power to obtain steep payment rates from insurers. Other factors, such as offering an important, unique service or access in a particular geographic area, can contribute to provider leverage as well. Even in markets with dominant health plans, insurers generally have not been aggressive in constraining rate increases, perhaps because the insurers can simply pass along the costs to employers and their workers. Although government intervention--through rate setting or antitrust enforcement--has its place, our findings suggest a range of market and regulatory approaches should be examined in any attempt to address the consequences of growing provider market clout.

Because many services performed in hospitals can safely and conveniently be performed in ambulatory settings, physicians have become owners of entities directly competing with hospitals for patients in a new medical arms race. Hospitals and medical staff physicians face growing tensions as a result of physicians' growing reluctance to take emergency department call and the consequences of hospitalists replacing physicians in the care of inpatients. Although there are increasing expectations that health system challenges will lead hospitals and physicians to collaborate, in many markets the willingness and ability for hospitals and physicians to work together is actually eroding.

Unintended overpayment of some services, in combination with other market factors, is driving increased use of expensive care, which in turn could be an important driver of health care cost trends. Reimbursement systems are highly dependent on provider charge data that rarely provide accurate and up-to-date indicators of relative costs. As a result, newer services, in which productivity is increasing over time, tend to be more lucrative. As the largest payer, and one whose reimbursement policies are followed by private insurers and Medicaid programs, Medicare can address this issue by taking steps to make its prospective payment rates reflect relative costs more accurately.

Local policymakers should examine the factors that facilitate the proliferation of services, especially the development of small NICUs. Policies that encourage cooperative efforts by hospitals should be developed. Eliminating small NICUs would not restrict the NICU bed supply in most metropolitan statistical areas.