Prepaid plans provide an increasingly large share of today's health care in the United States. At present, 27.7 million people are enrolled in health maintenance organizations (HMOs), as compared with 10.5 million five years ago.* Of these, 44.2 percent are now enrolled in for-profit plans. Certain of these plans include controversial features to limit the use of services: a primary physician who serves as a gatekeeper to control specialty referrals, and financial incentives and disincentives held out to individual physicians and based on the case-by-case or annual cost of services.I believe that such referral restrictions and financial incentives should . . .