Study shows little insurer competition

Most commercial health insurance markets in the United States are dominated by one or two health insurers, according to an updated analysis released by the American Medical Association.

The 2010 edition of "Competition in Health Insurance: A Comprehensive Study of U.S. Markets" found that 99% of health insurance markets in the United States are "highly concentrated," based on the 1997 U.S. Department of Justice and Federal Trade Commission Horizontal Merger Guidelines.

In 48% of metropolitan statistical areas, at least one insurer had a market share of 50% or more. In 60% of the areas, the two largest insurers had a combined market share of 70% or greater. In 24 states, the two largest insurers had a combined market share of 70% or more.