Competition lacking among insurers

In 24 of 43 U.S. states, the two largest health insurers had a combined market share of 70 percent or more, according to an analysis released in March by the American Medical Association.

The AMA report, "Competition in Health Insurance: A Comprehensive Study of U.S. Markets," analyzed 43 states and 313 metropolitan markets against an index used by federal regulators for measuring market concentration. Last year, 18 of 42 states had two insurers with a combined market share of 70 percent or more.

The analysis found 99 percent of metropolitan markets are "highly concentrated," with a few dominant insurers, up from 94 percent metropolitan markets last year. In 54 percent of metropolitan markets, at least one insurer had a market share of 50 percent or greater, up from 40 percent of metropolitan markets the year before.