A new study shows that anticompetitive market power is widespread for each of the three most popular managed health care plans in the United States, and it's hurting both patients and physicians while contributing to higher health costs.

The report, issued by the American Medical Association, found that a "significant absence of health insurer competition" is present in 70 percent of metropolitan areas. The AMA's annual health insurance market analysis for the first time examines insurer competition in the markets for point-of-service plans, in addition to its annual analysis of health maintenance organizations and preferred provider organizations.

The study, which looked at 385 metropolitan areas in all 50 states, said that about 68 percent of the metropolitan areas studied by the AMA had one insurance company with a combined market share of 50 percent or more among HMOs, PPOs and POSs.