Concentration in Health Insurance Markets


About two-thirds of Americans received health insurance through private plans in 2022. People may enroll in these private insurance plans through various markets, including:

  • The individual health insurance market, which offers coverage directly to individuals. The individual exchanges, a subset of the overall individual market, are marketplaces in each state operated by the state or federal government. You can also view overall individual market and individual exchange enrollment data by state..
  • The small-group health insurance market, which offers coverage through small employers.
  • The large-group health insurance market, which offers coverage through large employers.

In this report, we find that private health insurance markets overall were concentrated from 2011 through 2022; most people who enrolled in a private health insurance plan did so with one of a small number of insurance companies. However, the markets for individuals became slightly less concentrated from 2020 through 2022. This concentration in the health insurance market can lead to increases in insurance premiums, which can reduce patients' access to affordable health insurance.

This interactive map provides information on health insurance markets by year and market type. Select a market type (e.g., Small-Group Market) and year (e.g., 2011) to see country-wide data and the associated data table. You can also hover over a state to see more detailed information. Clicking on the play button or moving the slider under the map will show you how the data changes over time for a market type. You can also download the data used in this graphic.



Individual Exchange Market

Legend
Largest three issuers hold less than 80% market share
Largest three issuers hold 80-100% market share. Darker blue indicates that this number is closer to 100%.

Source: GAO analysis of data from the Centers for Medicare & Medicaid Services (CMS). | GAO-25-107194


The table below displays data for the selected market and year. Click here to download the data used in this graphic.


State Year No. of Issuers Weighted Avg No. of Issuers Largest Issuer Largest Issuer Market Share (%) Second Largest Issuer Second Largest Issuer Market Share (%) Third Largest Issuer Third Largest Issuer Market Share (%) Combined Market Share of 3 Largest Issuers (%) Weighted Avg Market Share of Largest Issuer Across Rating Areas (%) Change in Largest Issuer Market Share across Rating Areas, 2015-2022 (%)
Alabama 2016 3 2.4 BCBS OF ALABAMA GRP 67 UNITEDHEALTH GRP 23 HUMANA GRP 9 100 68 12
Alaska 2016 2 2 OREGON DENTAL GRP 70 PREMERA BLUE CROSS GRP 30 -- -- 100 70 24
Arizona 2016 8 6.3 UNITEDHEALTH GRP 38 BCBS OF ARIZONA INC 20 PHOENIX HEALTH PLANS INC 18 76 42 11
Arkansas 2016 4 4 ARKANSAS BCBS GRP 92 CENTENE CORP GRP 6 CATHOLIC HLTH INITIATIVES GRP 2 99 92 -43
California 2016 12 5.3 BLUE SHIELD OF CALIFORNIA GRP 30 WELLPOINT INC GRP 25 KAISER FOUNDATION GRP 23 79 43 7
Colorado 2016 8 6.7 KAISER FOUNDATION GRP 42 WELLPOINT INC GRP 26 CIGNA HEALTH GRP 11 79 54 -26
Connecticut 2016 4 4 HIP INS GRP 51 WELLPOINT INC GRP 36 HEALTHYCT INC 11 98 63 38
Delaware 2016 2 2 HIGHMARK GRP 90 AETNA GRP 10 -- -- 100 90 9
District of Columbia 2016 2 2 CAREFIRST INC GRP 86 KAISER FOUNDATION GRP 14 -- -- 100 86 0
Florida 2016 7 4.4 BCBS OF FLORIDA INC 40 AETNA GRP 16 MOLINA HEALTHCARE INC GRP 16 72 62 -16
Georgia 2016 8 6.9 HUMANA GRP 32 CENTENE CORP GRP 18 WELLPOINT INC GRP 18 69 38 -14
Hawaii 2016 2 2 HAWAII MEDICAL SERVS ASSOC 58 KAISER FOUNDATION GRP 42 -- -- 100 58 --
Idaho 2016 5 5 BLUE CROSS OF IDAHO HEALTH SERVS INC 44 IHC INC GRP 32 MONTANA HEALTH COOP 16 92 49 -4
Illinois 2016 7 5.2 HCSC GRP 57 AETNA GRP 10 CENTENE CORP GRP 10 77 61 -24
Indiana 2016 8 6.7 WELLPOINT INC GRP 30 MDWISE MARKETPLACE INC 19 CARESOURCE MANAGEMENT GRP 16 66 33 24
Iowa 2016 4 3.4 AETNA GRP 73 UNITEDHEALTH GRP 24 MEDICA GRP 3 100 76 -33
Kansas 2016 3 2.4 BCBS OF KANSAS GRP 62 BCBS OF KC GRP 23 UNITEDHEALTH GRP 15 100 83 -6
Kentucky 2016 7 6.4 WELLPOINT INC GRP 63 CARESOURCE MANAGEMENT GRP 16 HUMANA GRP 9 87 63 10
Louisiana 2016 4 3.5 LOUISIANA HEALTH SERVS GRP 48 UNITEDHEALTH GRP 25 HUMANA GRP 17 89 50 61
Maine 2016 3 3 MAINE COMM HEALTH OPTIONS 68 WELLPOINT INC GRP 18 HARVARD PILGRIM HTH CARE GRP 14 100 68 -46
Maryland 2016 5 5 CAREFIRST INC GRP 65 KAISER FOUNDATION GRP 20 UNITEDHEALTH GRP 8 93 65 -18
Massachusetts 2016 10 10 TUFTS HEALTH PLAN 47 NEIGHBORHOOD HEALTH PLAN INC 24 BOSTON MEDICAL CENTER HEALTH PLAN INC 16 87 47 28
Michigan 2016 11 6.2 BCBS OF MICHIGAN GRP 56 SPECTRUM HEALTH GRP 23 HUMANA MEDICAL PLAN OF MICHIGAN INC 10 88 58 -23
Minnesota 2016 4 3.7 BCBS OF MN GRP 28 HEALTHPARTNERS GRP 27 UCARE MINNESOTA 23 78 44 --
Mississippi 2016 3 2.9 CENTENE CORP GRP 50 HUMANA GRP 27 UNITEDHEALTH GRP 23 100 54 44
Missouri 2016 6 3.7 AETNA GRP 36 WELLPOINT INC GRP 19 UNITEDHEALTH GRP 17 71 52 -12
Montana 2016 3 3 HCSC GRP 62 MONTANA HEALTH COOP 27 PACIFICSOURCE HEALTH PLAN GRP 11 100 62 -8
Nebraska 2016 4 4 AETNA GRP 48 BCBS OF NEBRASKA 27 UNITEDHEALTH GRP 19 94 48 -20
Nevada 2016 3 2.9 UNITEDHEALTH GRP 56 WELLPOINT INC GRP 31 SAINT MARYS HEALTH CARE CORP GRP 13 100 63 6
New Hampshire 2016 5 5 WELLPOINT INC GRP 46 MINUTEMAN HEALTH INC 30 HARVARD PILGRIM HTH CARE GRP 20 96 46 -19
New Jersey 2016 5 5 BCBS OF NJ GRP 60 INDEPENDENCE HEALTH GRP INC 21 MULBERRY HLTH GRP 9 90 60 9
New Mexico 2016 4 4 MOLINA HEALTHCARE INC GRP 40 NEW MEXICO HEALTH CONNECTIONS 32 PRESBYTERIAN HEALTHCARE SERVS GRP 22 93 44 -3
New York 2016 15 8.8 NEW YORK STATE CATHOLIC HEALTH PLAN INC 26 WELLPOINT INC GRP 11 MULBERRY HLTH GRP 10 47 28 90
North Carolina 2016 3 2.7 BCBS OF NORTH CAROLINA 47 UNITEDHEALTH GRP 29 AETNA GRP 24 100 60 -11
North Dakota 2016 3 3 NORIDIAN MUTUAL INS CO 54 MEDICA GRP 25 SANFORD HEALTH PLAN/SANFORD HEALTH PLAN OF MINNESOTA 21 100 60 -15
Ohio 2016 14 9.8 CARESOURCE MANAGEMENT GRP 29 MEDICAL MUTUAL OF OHIO 22 WELLPOINT INC GRP 13 63 39 -13
Oklahoma 2016 2 2 HCSC GRP 95 UNITEDHEALTH GRP 5 -- -- 100 95 -26
Oregon 2016 10 7.7 PROVIDENCE HEALTH PLAN 51 OREGON DENTAL GRP 21 PREMERA BLUE CROSS GRP 10 82 56 2
Pennsylvania 2016 8 4 INDEPENDENCE HEALTH GRP INC 31 HIGHMARK GRP 18 UPMC HEALTH OPTIONS INC 18 67 64 -4
Rhode Island 2016 3 3 BCBS OF RHODE ISLAND 48 NEIGHBORHOOD HLTH PLAN OF RI INC 47 UNITEDHEALTH GRP 4 100 48 54
South Carolina 2016 3 1.7 BCBS OF SC GRP 95 AETNA GRP 4 UNITEDHEALTH GRP 0 100 95 20
South Dakota 2016 2 2 AVERA HEALTH PLANS INC 73 SANFORD HEALTH PLAN/SANFORD HEALTH PLAN OF MINNESOTA 27 -- -- 100 73 3
Tennessee 2016 4 3.1 BCBS OF TN INC 66 UNITEDHEALTH GRP 17 HUMANA GRP 9 92 66 -46
Texas 2016 16 7.3 HCSC GRP 40 UNITEDHEALTH GRP 12 MOLINA HEALTHCARE INC GRP 12 64 44 -44
Utah 2016 4 3.1 IHC INC GRP 62 MOLINA HEALTHCARE INC GRP 33 HUMANA GRP 4 99 62 51
Vermont 2016 2 2 BCBS OF VT GRP 88 MVP GRP 12 -- -- 100 88 -44
Virginia 2016 8 5.3 WELLPOINT INC GRP 38 AETNA GRP 15 KAISER FOUNDATION GRP 15 68 51 9
Washington 2016 10 7.7 PREMERA BLUE CROSS GRP 39 CENTENE CORP GRP 19 GRP HEALTH COOP GRP 17 75 40 -33
West Virginia 2016 2 1.3 HIGHMARK GRP 96 CARESOURCE WEST VIRGINIA CO 4 -- -- 100 96 -33
Wisconsin 2016 15 6.9 MOLINA HEALTHCARE INC GRP 28 DEAN HEALTH GROUP 17 SECURITY HEALTH PLAN OF WISCONSIN INC 12 58 54 6
Wyoming 2016 1 1 BCBS OF WYOMING 100 -- -- -- -- 100 100 40

  • Our analysis includes the 50 states and the District of Columbia.
  • Federal law defines a small employer as having an average of 1 to 50 employees during the preceding calendar year; however, states may apply this definition based on an average of 1 to 100 employees.
  • Where multiple issuers in a state shared a parent company, we aggregated the individual issuers to the parent company level. We calculated issuers' market share using covered life-years that issuers reported to Centers for Medicare & Medicaid Services or states. This measure is calculated as the average number of lives insured each month in the reporting year. Rather than a point-in-time measurement, this measure accounts for changes in enrollment that occur throughout the year.
  • This table presents two calculations of individual exchange market share, one unweighted and one weighted. "Market share" refers to the unweighted ratio of the enrollment for each issuer in a state to the total enrollment in that state. "Weighted average market share across rating areas" refers to average market share of an issuer across a state's rating areas, which are geographic areas established by states and used, in part, by issuers to set premium rates, weighted by the number of covered life-years in each rating area.
  • Covered life-years is one of several ways to measure health insurance enrollment, so it may differ from other measures of market size.
  • Names for some issuers have changed over time. For the purposes of this graphic, we have presented the issuer name associated with a given year.
  • We rounded market share values of less than 0.5 percent to zero.
  • Hawaii and Minnesota are not included in this figure for 2015 because we were unable to obtain data for that year. The remaining 49 states, including the District of Columbia, are included in 2015, and Hawaii and Minnesota are included for later years.