Has the sky-high cost of health care almost priced you out of making doctor's visits? Rising co-payments and other out-of-pocket expenses, as well as increasing monthly premiums for health insurance, can be traced in many instances to the increased lack of competition among health insurance providers.

A recent study by the American Medical Association (AMA) reports that, among 313 metropolitan markets in the United States, 99 percent are "highly concentrated." That means consumers in those areas have little or no choice when it comes to health insurance plans.

In 55 percent of the 43 states surveyed in the AMA report, the two largest insurers combined garnered a 70 percent or better market share. Dr. James Rohack, president of the AMA, says that in areas with consolidated markets, "patient premiums, deductibles and co-payments have soared without an increase in benefits."

Put another way, it's almost certain that the dominant health insurance providers in your market have boosted premiums and increased other expenses without providing better or additional services.

The health insurance reform organization Health Care for Americans Now (HCAN) reports that insurance premiums rose 87 percent on average over the past six years -- and that in little more than a decade, there were more than 400 corporate mergers involving health insurers. Consolidations have led to market practices that hurt the consumer but have yielded sizable corporate profits. According to HCAN, from 2000 to 2007, profit margins for the largest publicly traded health insurers soared 428 percent.

Let's use Rhode Island as an example: Blue Cross Blue Shield of Rhode Island and UnitedHealth Group, Inc. together control 95 percent of market share in that state. HCAN, citing a 2008 report by Northwest Federation of Community Organizations, notes that health insurance premiums there rose 83 percent from 2000 to 2007--and Blue Cross Blue Shield's profits rose 331 percent from 2004 to 2007.

Each state has a similar tale. The lack of competition amongst health insurance providers in our cities has exposed the pocketbooks of consumers to corporate plunder. It remains to be seen what the effect of health reform will be on health insurer market concentration.