"Data from the American Medical Association show that in each of 43 states, a handful of top insurers have gained such a stronghold that their markets are considered "highly concentrated" under U.S. Department of Justice guidelines, often far exceeding the thresholds that trigger antitrust concerns."
There have been more than 400 mergers leading to monopoly and monopsony in many states.
Yikes!
Link
The Justice Department has been contacted by the AMA about marketplace abuse but there has been no response. In 24 major cities, and the state of North Dakota, the HMO's have monopoly power.
The results are predictable, increases in price, reduction of choice, and poorer service.