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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 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 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 (%) Change in 3 Largest Issuer Market Share, 2011-2022 (%)
Alabama 2015 16 BCBS OF ALABAMA GRP 86 UNITEDHEALTH GRP 11 HUMANA GRP 3 99 3
Alaska 2015 10 OREGON DENTAL GRP 48 PREMERA BLUE CROSS GRP 44 ASSURANT INC GRP 6 98 31
Arizona 2015 23 BCBS OF ARIZONA INC 42 CENTENE CORP GRP 19 UNITEDHEALTH GRP 14 75 -1
Arkansas 2015 18 ARKANSAS BCBS GRP 74 CENTENE CORP GRP 12 CATHOLIC HLTH INITIATIVES GRP 11 97 9
California 2015 31 WELLPOINT INC GRP 31 BLUE SHIELD OF CALIFORNIA GRP 26 KAISER FOUNDATION GRP 26 82 1
Colorado 2015 24 COLORADO HEALTH INS COOP INC 23 KAISER FOUNDATION GRP 22 WELLPOINT INC GRP 19 64 30
Connecticut 2015 15 HIP INS GRP 45 WELLPOINT INC GRP 32 HEALTHYCT INC 10 87 18
Delaware 2015 13 HIGHMARK GRP 93 AETNA GRP 6 UNITEDHEALTH GRP 1 99 18
District of Columbia 2015 13 CAREFIRST INC GRP 81 KAISER FOUNDATION GRP 12 AETNA GRP 3 96 14
Florida 2015 30 BCBS OF FLORIDA INC 34 HUMANA GRP 17 AETNA GRP 15 66 12
Georgia 2015 25 HUMANA GRP 43 AETNA GRP 23 WELLPOINT INC GRP 20 85 4
Hawaii 2015 9 HAWAII MEDICAL SERVS ASSOC 57 KAISER FOUNDATION GRP 42 AMERICAN INTL GRP 1 100 1
Idaho 2015 17 BLUE CROSS OF IDAHO HEALTH SERVS INC 60 IHC INC GRP 16 MONTANA HEALTH COOP 13 89 -4
Illinois 2015 25 HCSC GRP 81 LAND OF LINCOLN MUTUAL HEALTH INS CO 5 UNITEDHEALTH GRP 4 89 10
Indiana 2015 23 WELLPOINT INC GRP 42 UNITEDHEALTH GRP 23 CENTENE CORP GRP 10 75 16
Iowa 2015 19 WELLMARK GRP 68 AETNA GRP 26 UNITEDHEALTH GRP 3 98 7
Kansas 2015 20 BCBS OF KANSAS GRP 42 AETNA GRP 37 BCBS OF KC GRP 14 94 20
Kentucky 2015 21 WELLPOINT INC GRP 52 KENTUCKY HEALTH COOP 32 HUMANA GRP 10 94 3
Louisiana 2015 22 LOUISIANA HEALTH SERVS GRP 65 UNITEDHEALTH GRP 13 LOUISIANA HEALTH COOP INC 9 86 14
Maine 2015 12 MAINE COMM HEALTH OPTIONS 71 WELLPOINT INC GRP 27 HARVARD PILGRIM HTH CARE GRP 1 99 8
Maryland 2015 18 CAREFIRST INC GRP 86 KAISER FOUNDATION GRP 8 UNITEDHEALTH GRP 3 97 13
Massachusetts 2015 25 TUFTS HEALTH PLAN 30 BCBS OF MA GRP 21 NEIGHBORHOOD HEALTH PLAN INC 21 72 -6
Michigan 2015 29 BCBS OF MICHIGAN GRP 56 SPECTRUM HEALTH GRP 13 UNITEDHEALTH GRP 8 78 14
Minnesota 2015 25 BCBS OF MN GRP 68 HEALTHPARTNERS GRP 18 MEDICA GRP 4 90 -3
Mississippi 2015 18 MISSISSIPPI INS GRP 39 CENTENE CORP GRP 22 UNITEDHEALTH GRP 20 81 9
Missouri 2015 23 AETNA GRP 46 WELLPOINT INC GRP 20 UNITEDHEALTH GRP 15 80 14
Montana 2015 16 HCSC GRP 57 MONTANA HEALTH COOP 23 PACIFICSOURCE HEALTH PLAN GRP 12 92 17
Nebraska 2015 19 BCBS OF NEBRASKA 49 AETNA GRP 32 UNITEDHEALTH GRP 11 92 7
Nevada 2015 18 UNITEDHEALTH GRP 50 WELLPOINT INC GRP 20 NEVADA HEALTH COOP 13 83 -6
New Hampshire 2015 14 WELLPOINT INC GRP 65 HARVARD PILGRIM HTH CARE GRP 13 MINUTEMAN HEALTH INC 12 90 7
New Jersey 2015 19 BCBS OF NJ GRP 56 INDEPENDENCE HEALTH GRP INC 19 FREELANCERS COOP OF NEW JERSEY 15 91 8
New Mexico 2015 18 HCSC GRP 43 NEW MEXICO HEALTH CONNECTIONS 26 PRESBYTERIAN HEALTHCARE SERVS GRP 24 93 -15
New York 2015 34 FREELANCERS HEALTH SERVS CORP 19 WELLPOINT INC GRP 12 AMERICAN INTL GRP 11 42 -1
North Carolina 2015 18 BCBS OF NORTH CAROLINA 75 AETNA GRP 15 UNITEDHEALTH GRP 8 98 -2
North Dakota 2015 12 NORIDIAN MUTUAL INS CO 78 MEDICA GRP 10 ASSURANT INC GRP 7 95 11
Ohio 2015 28 MEDICAL MUTUAL OF OHIO 37 WELLPOINT INC GRP 20 CARESOURCE MANAGEMENT GRP 10 67 -30
Oklahoma 2015 21 HCSC GRP 88 UNITEDHEALTH GRP 7 ASSURANT INC GRP 2 97 8
Oregon 2015 25 OREGON DENTAL GRP 41 PREMERA BLUE CROSS GRP 17 PROVIDENCE HEALTH PLAN 12 70 10
Pennsylvania 2015 31 HIGHMARK GRP 45 INDEPENDENCE HEALTH GRP INC 23 UPMC HEALTH OPTIONS INC 8 77 8
Rhode Island 2015 9 BCBS OF RHODE ISLAND 59 NEIGHBORHOOD HLTH PLAN OF RI INC 37 UNITEDHEALTH GRP 4 100 0
South Carolina 2015 17 BCBS OF SC GRP 51 CONSUMERS CHOICE HEALTH INS CO 27 AETNA GRP 12 90 18
South Dakota 2015 14 WELLMARK GRP 62 SOUTH DAKOTA STATE MEDICAL HOLDING CO INC 17 AVERA HEALTH PLANS INC 15 93 12
Tennessee 2015 20 BCBS OF TN INC 63 TRH HEALTH INS CO 16 COMM HEALTH ALLIANCE MUTUAL INS CO 8 87 -15
Texas 2015 37 HCSC GRP 65 HUMANA GRP 12 UNITEDHEALTH GRP 8 85 -19
Utah 2015 17 IHC INC GRP 51 HUMANA GRP 16 ARCHES MUTUAL INS CO 14 80 8
Vermont 2015 6 BCBS OF VT GRP 89 MVP GRP 10 AMERICAN INTL GRP 0 100 1
Virginia 2015 26 WELLPOINT INC GRP 53 AETNA GRP 11 KAISER FOUNDATION GRP 10 73 -9
Washington 2015 24 PREMERA BLUE CROSS GRP 48 REGENCE GRP 16 GRP HEALTH COOP GRP 14 79 -25
West Virginia 2015 18 HIGHMARK GRP 91 UNITEDHEALTH GRP 7 ASSURANT INC GRP 1 98 28
Wisconsin 2015 32 WISCONSIN PHYSICIANS SERVS INS GRP 14 DEAN HEALTH GRP 13 UNITEDHEALTH GRP 13 40 -3
Wyoming 2015 14 BCBS OF WYOMING 59 WINHEALTH PARTNERS 27 ASSURANT INC GRP 7 93 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.
  • Small and large employers may offer fully insured group plans (by purchasing coverage from an issuer) or self-funded group plans (by setting aside funds to pay for employee health care). Most small employers purchase fully insured plans, while most large employers self-fund at least some of their employee health benefits. For the small-group and large-group markets, enrollment data are from fully insured plans only.
  • 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, which measure the average number of lives insured, including dependents, on a pre-specified day of each month of the 12 months in the reporting year. Rather than a point-in-time measurement, this measure accounts for changes in enrollment that occur throughout the year. Market share refers to the ratio of the enrollment for each issuer in a state to the total enrollment in that state.
  • 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.