The vast majority of Medicare Advantage markets are highly concentrated, according to the American Medical Association's annual Competition in Health Insurance report.
In 91% of MA markets, one insurer controls at least 30% of the market, and in 30% of markets, the largest insurer controls more than 50% of the market.
Medicare Advantage markets have remained steadily concentrated over time, according to the AMA. The percentage of highly-concentrated MA markets has hovered between 97% and 99% since 2017, the association found.
UnitedHealth Group is the largest Medicare Advantage insurer overall, with a national market share of 29%.
Here are the 32 markets where the largest insurer controls less than 30% of the market:
Carbondale-Marion, Ill.
Carle Health: 21%
Worcester, Mass.-Conn.
Point32Health: 22%
Bangor, Maine
Martin's Point Healthcare: 24%
Canton-Massillon, Ohio
UnitedHealth Group: 24%
Baltimore-Columbia-Towson, Md.
Kaiser Permanente: 25%
Springfield, Mass.
Commonwealth Care Alliance: 25%
Minneapolis-St. Paul-Bloomington, Minn.-Wis.
BCBS Minnesota: 25%
Allentown-Bethlehem-Easton, Pa.-N.J.
Aetna: 25%
Yuma, Ariz.
Centene: 26%
Kankakee, Ill.
Humana: 26%
Santa Fe, N.M.
UnitedHealth Group: 26%
Elmira, N.Y.
Lifetime Healthcare: 26%
Glens Falls, N.Y.
Humana: 26%
Cincinnati, Ohio-Ky.-Ind.
Humana: 26%
Wheeling, W.V.-Ohio
Humana: 26%
Homosassa Springs, Fla.
UnitedHealth Group: 27%
Grand Forks, N.D.-Minn.
Medica: 27%
Toledo, Ohio
Aetna: 27%
Reading, Pa.
Aetna: 27%
New York-Newark-Jersey City, N.Y.-N.J.-Pa.
UnitedHealth Group: 28%
Akron, Ohio
UnitedHealth Group: 28%
Columbus, Ohio
CVS: 28%
Mansfield, Ohio
UnitedHealth Group: 28%
Philadelphia-Camden-Wilmingon, Pa.-N.J.-Del.-Md.
Aetna: 28%
Memphis, Tenn.-Miss.-Ark.
Humana: 28%
Weirton-Steubenville, W.V.-Ohio
Aetna: 28%
Coeur d'Alene, Idaho
Blue Cross of Idaho: 29%
Portland-Vancouver-Hillsboro, Ore.-Wash.
Kaiser Permanente: 29%
East Stroudsburg, Pa.
Aetna: 29%
Clarksville, Tenn.-Ky.
Humana: 29%
Jackson, Tenn.
BCBS Tennessee: 29%
Nashville-Davidson-Mufressboro-Franklin, Tenn.
Cigna: 29%
See the full report here.