A January 2017 Health Affairs article concludes that the bigger the health insurer, the lower the prices it can negotiate from physician groups.  The findings are evidence that consolidation among health insurers  affects  payments to physicians

Large insurers with market shares of 15% paid 21% less than small insurers with shares of less than 5% of a market.

The Modern Healthcare bottom line: “Bigger insurers have this bargaining power they are using to negotiate lower prices,” said Eric T. Roberts,a postdoctoral fellow in the Department of Health Care Policy at Harvard Medical School who authored the study.

The researchers utilized FAIR Health and looked at 15 million doctors’ visits in 2014.