The proposed merger between health insurers Aetna and Humana would give the combined company 25% of Medicare Advantage enrollment nationwide, assuming no divestitures were required, according to a new report by the Kaiser Family Foundation. The proposed merger of Anthem and Cigna would give those insurers about 6% of MA market share in comparison. “However, the effects of mergers are likely to vary substantially across states and even within states based on locality depending on where Medicare Advantage firms offer their plans and how many beneficiaries are enrolled in them,” the report notes. “For example, Anthem (which was formerly known as Wellpoint) gained scale when it merged with BCBS licensees in a number of states. It now offers its Medicare Advantage plans through its BCBS affiliated plans…as well as through independently licensed products.” The report reviews national and state-level MA enrollment trends as of March, as well as recent data on MA premiums, cost sharing and quality ratings. In letters last year to the departments of Justice and Health and Human Services, the AHA said Aetna’s proposed acquisition of Humana and Anthem’s proposed acquisition of Cigna “have the very real potential to reduce competition substantially, increase the cost of premiums, and diminish the insurers’ willingness to be innovative partners with providers and consumers in transforming health care.”