Blanket coverage: a few insurers dominate most markets across the state, which the AM A says can lead to unhealthy competition.

• Position: Statewide

Bigger is often better in business. Size can lend greater efficiency to an enterprise, leading to lower prices. But unchecked, companies can bulk up into bullies that boost prices artificially. According to a study by the American Medical Association, the U.S. health-insurance industry--specifically its health-maintenance and preferred-provider organizations--is ripe for such abuses because only one or two insurers dominate most local markets. The study calls for greater scrutiny of future mergers and their anti-competitive effects. Lew Borman, a spokesman for the state's dominant health insurer, doesn't agree, noting that Blue Cross and Blue Shield of North Carolina goes up against dozens of competitors. Its market share, he says, results from its offerings and performance, not its size. "We're out there every day with a very active sales force that understands North Carolina customers and their health-care needs."

Only 11 states ranked higher in the percentage of the combined HMO-PPO market held by the top two insurers on Jan. 1, 2008, the most recent data available. Largest share Second-largest share Top two Alabama 93% 3% 96% Hawaii 75 21 96 Alaska 77 16 93 Rhode Island 69 22 91 Iowa 77 12 89 South Carolina 67 16 83 Mississippi 66 16 82 Tennessee 70 11 81 Nebraska 66 15 81 Idaho 69 11 80 Illinois 72 8 80 North...