Chicago-based WellPoint commands the health insurance market in a majority of metropolitan areas, according to an American Medical Association annual study of health insurer competition.
In 82 of the 388 metropolitan areas studied by the AMA, WellPoint was the largest health insurer, dominating market shares in roughly 21 percent of the areas studied.
Leading in 37 metropolitan areas, the second largest health insurer by market share is Chicago-based Health Care Service. Minnetonka, Minn.-based UnitedHealth Group is the third largest health insurer by market share, leading in 35 areas.
The AMA study also found there's a considerable lack of health insurer competition in 72 metropolitan areas. Additionally, 17 states have a single health insurer that dominates 50 percent or more of commercial market shares.
Data used in the AMA study was based on 2012 commercial enrollment in fully and self-insured plans and participation in consumer-driven health plans.