Most Medicare Advantage Beneficiaries Live In Highly Concentrated Markets With Few Plan Choices

About 89% of Medicare beneficiaries in 2024 lived in a county where at least half of beneficiaries were enrolled in Medicare Advantage plans sponsored by only one or two insurers, making the market share highly concentrated, according to a recent analysis. About 4% of beneficiaries lived in a county considered a very highly concentrated market, defined as one in which a single insurer held at least 50% of Medicare Advantage enrollment.

The researchers analyzed data from the Centers for Medicare & Medicaid Services (CMS) Medicare Advantage Enrollment, Benefit, and Landscape files for 2010 to 2024. They used the Herfindahl-Hirschman . . .