The study, which looked at 385 metropolitan statistical areas, said nearly two in five metropolitan areas had one insurance company with a combined market share of 50 percent or more among health maintenance organization (HMO), point-of-service (POS) and preferred provider organization (PPO) plans.

FORBES: AMA: 70 Percent Of U.S. Lacks Health Insurance Competition

"The need for a smaller network with lower pricing was critical, " said Juan Davila, an executive vice president at Blue Shield of California, which said it hopes to offer a preferred-provider-organization plan for individuals on the exchange.

WSJ: Hospitals Forge New Deals With Insurers