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Data Note: Medicare Advantage Enrollment, by Firm, 2015

Updated county-level data showing market share by firm for 2016 is available here.

In recent weeks, a number of potential mergers and acquisitions between large firms that offer health insurance have been reported in the press, including the July 3, 2015 announcement of a merger between Aetna and Humana. These mergers could affect consumers in the individual market, enrollees in the new federal and state Marketplaces, employees with employer-sponsored insurance, as well as people covered by public programs such as Medicare. Nearly 17 million Medicare beneficiaries – almost one-third of the total Medicare population – are enrolled in private Medicare plans, known as Medicare Advantage plans, raising questions about the potential impact of these mergers on Medicare enrollees.

This Data Note examines the Medicare Advantage market share of large firms that have reportedly engaged in merger and acquisition discussions: Aetna, Anthem, Cigna, Humana, and UnitedHealthcare. Table 1 shows the Medicare Advantage market shares of these five firms nationally and by state. Table 2 highlights the counties in which the Aetna-Humana merger could have a relatively large impact on Medicare Advantage enrollees based on the combined market share of these two firms. Table 3 shows the market share of these five firms in the 50 counties with the largest number of Medicare Advantage enrollees. This Data Note uses Medicare Advantage enrollment data released by the Centers for Medicare and Medicaid Services in March 2015.

Table 1 shows the market share of the five large firms, nationally and by state, that have reportedly been engaged in merger and acquisition discussions. Together, these five firms comprise more than half (52%) of the Medicare Advantage market (Figure 1).

Figure 1: Medicare Advantage Market Share of Five Firms Reported to Be Discussing Mergers

Figure 1: Medicare Advantage Market Share of Five Firms Reported to Be Discussing Mergers

If the announced deal between Aetna and Humana proceeds, the consolidated firm would provide coverage to more than one-quarter (26%) of all Medicare Advantage enrollees nationwide, making it the leading Medicare Advantage insurer, ahead of UnitedHealthcare, which has 20 percent of all Medicare Advantage enrollees.

Mergers between insurers would play out differently across the country because Medicare Advantage market share by firm varies greatly across states and counties. In some counties and states, locally-owned firms play a larger role in the Medicare Advantage market than national firms, while other states are dominated by the large, national firms.

  • Based on current enrollment numbers, the combined market share of Aetna and Humana would include at least half of all Medicare Advantage enrollees in 10 states and at least two-thirds of all enrollees in five states (KS, LA, MS, VA, and WV), unless they divest some Medicare Advantage plans in response to regulatory (antitrust) issues. By itself, Humana has more than half of the Medicare Advantage market in five states (KY, LA, MS, VA, and WV), including two states (MS and WV) in which it has more than two-thirds of all Medicare Advantage enrollees. Aetna has at least one-quarter of all enrollees in eight states (AK, DE, IA, KS, ME, MO, NE, and NJ).
  • UnitedHealthcare currently has more than half of the market in four states (NE, NH, VT, and WY), including two states (VT and WY) in which it has more than two-thirds of the market. UnitedHealthcare has more than one-quarter of all enrollees in 19 other states and the District of Columbia. Anthem more than one-fifth of the market (23%) in Ohio. Cigna has more than one-third of the market (38%) in Delaware and about one-fifth of the market in three other states (TN, AL, and MD).

In seven states (CT, ME, MA, MT, NM, ND and SD), the firm with the most Medicare Advantage enrollees is a locally operated firm and thus mergers among the large, national firms would likely have a smaller impact in these states.

Table 2 and Figure 2 drill down to the county level to show the counties in which Humana and Aetna currently account for at least 50 percent of the Medicare Advantage market.

Figure 2: Together, Aetna and Humana would have at least 50% of the Medicare Advantage market in 39 counties

Figure 2: Together, Aetna and Humana would have at least 50% of the Medicare Advantage market in 39 counties

Among the 335 counties nationwide with at least 10,000 Medicare Advantage enrollees:

  • Humana currently provides coverage to at least half of all Medicare Advantage enrollees in 21 counties, and at least two-thirds of all Medicare Advantage enrollees in six counties;
  • Aetna currently provides coverage to more than half of all Medicare Advantage enrollees in two counties: Polk County, Iowa which includes Des Moines and Sedgwick County, Kansas which includes Wichita; and
  • Together, Aetna and Humana currently cover at least half of all Medicare Advantage enrollees in 39 counties, and at least 75 percent of all Medicare Advantage enrollees in nine counties (Benton, AR; Polk County, IA; Winnebago County, IL; Johnson County, KS; Sedgwick County, KS; Livingston County, LA; Jackson County, MO; Anderson County, SC; and Kanawha County, WV).

Table 3 shows the Medicare Advantage market shares of the five large, national firms in 50 counties with the largest number of Medicare Advantage enrollees. Together, these 50 counties account for about one-third (34%) of all Medicare Advantage enrollees nationwide.

  • Humana has more enrollees than any other firm in 11 counties, while UnitedHealthcare has more enrollees than any other firm in 10 of the 50 counties. Anthem has a larger market share than any other firm in three counties. Cigna has the most Medicare Advantage enrollees in one of the 50 counties – Philadelphia County, PA.
  • Humana has at least half of all Medicare Advantage enrollees in three counties in Florida (Broward County, Palm Beach County, and Volusia County). UnitedHealthcare has at least half of all Medicare Advantage enrollees in six counties, three of which are in Texas (Pima County, AZ; Clark County, NV; Bexar County, TX; Dallas County, TX; Tarrant County, TX; and Milwaukee County, WI). Anthem has more than half of all Medicare Advantage enrollees in Suffolk County, NY.
  • Together, Aetna and Humana have more than half of all Medicare Advantage enrollees in six counties (Broward County, FL; Hillsborough County, FL; Palm Beach County, FL; Pasco County, FL; Volusia County, FL; and Franklin County, OH). In three of these six counties (Broward County, FL; Palm Beach County, FL; and Volusia County, FL), Humana already has at least half of all Medicare Advantage enrollees.

While the large, national firms have a substantial presence in many counties with a relatively large number of Medicare Advantage enrollees, none of these five large, national firms have the largest Medicare Advantage market share in 25 of the 50 counties.

Gretchen Jacobson and Tricia Neuman are with the Kaiser Family Foundation; and Anthony Damico is an independent consultant.

 Table 1: Medicare Advantage Market Share of the Five Firms Reported to be Discussing Mergers, by State, 2015
State Total Medicare Advantage Enrollment Percent of Enrollees in Firm’s Plans
Aetna Anthem Cigna Humana United-Healthcare All Others
Total U.S. 16,761,673 7% 3% 3% 19% 20% 48%
Alabama 238,091 0% 0% 22% 20% 16% 43%
Alaska 56 55% 0% 0% 0% 45% 0%
Arizona 425,454 1% 4% 10% 14% 37% 34%
Arkansas 114,326 6% 0% 2% 38% 29% 25%
California 2,127,666 1% 4% 0% 3% 16% 76%
Colorado 281,467 1% 0% 0% 14% 39% 46%
Connecticut 157,692 20% 3% 0% 0% 31% 46%
Delaware 13,841 40% 0% 38% 8% 12% 2%
District of Columbia 11,033 7% 0% 9% 0% 28% 56%
Florida 1,570,845 6% 2% 3% 37% 22% 30%
Georgia 460,670 9% 1% 4% 22% 49% 15%
Hawaii 110,465 0% 0% 0% 10% 19% 71%
Idaho 87,837 0% 0% 0% 10% 13% 77%
Illinois 371,007 11% 0% 5% 26% 39% 19%
Indiana 264,104 3% 14% 1% 35% 25% 21%
Iowa 81,541 40% 0% 0% 24% 24% 12%
Kansas 61,600 42% 0% 0% 48% 8% 1%
Kentucky 212,948 2% 17% 0% 60% 16% 5%
Louisiana 232,445 1% 0% 0% 65% 1% 33%
Maine 66,307 26% 2% 0% 7% 13% 52%
Maryland 76,375 10% 0% 19% 2% 13% 56%
Massachusetts 233,084 1% 0% 0% 0% 18% 81%
Michigan 595,239 1% 0% 0% 10% 1% 88%
Minnesota 480,474 0% 0% 0% 7% 0% 93%
Mississippi 76,776 1% 0% 11% 66% 1% 22%
Missouri 311,364 30% 2% 0% 22% 31% 15%
Montana 34,758 0% 0% 0% 20% 4% 76%
Nebraska 34,982 30% 0% 0% 16% 51% 3%
Nevada 146,094 4% 4% 0% 33% 45% 14%
New Hampshire 17,295 3% 12% 0% 17% 55% 14%
New Jersey 222,846 25% 3% 0% 0% 44% 27%
New Mexico 113,807 1% 2% 0% 13% 19% 65%
New York 1,212,239 5% 10% 0% 1% 18% 67%
North Carolina 512,924 8% 0% 1% 31% 34% 26%
North Dakota 17,878 0% 0% 0% 9% 1% 90%
Ohio 811,503 21% 23% 0% 29% 8% 19%
Oklahoma 111,013 3% 0% 0% 29% 29% 40%
Oregon 323,765 0% 0% 0% 1% 12% 87%
Pennsylvania 1,001,864 22% 0% 6% 4% 3% 65%
Puerto Rico 552,888 0% 0% 0% 9% 0% 91%
Rhode Island 71,009 0% 0% 0% 0% 28% 72%
South Carolina 209,812 2% 0% 4% 45% 45% 4%
South Dakota 26,400 7% 0% 0% 21% 1% 71%
Tennessee 412,042 1% 1% 22% 31% 18% 27%
Texas 1,098,678 12% 3% 10% 24% 33% 18%
Utah 113,034 8% 0% 0% 7% 45% 40%
Vermont 8,984 8% 0% 0% 0% 80% 12%
Virginia 206,427 4% 3% 0% 62% 18% 13%
Washington 348,467 0% 0% 0% 9% 25% 65%
West Virginia 99,454 14% 0% 0% 71% 2% 13%
Wisconsin 388,732 0% 1% 0% 19% 33% 47%
Wyoming 2,071 11% 0% 0% 4% 72% 12%

SOURCE: Kaiser Family Foundation analysis of CMS Medicare Advantage enrollment files for March 2015.

Table 2: Market Shares of Aetna and Humana in Counties in Which the Combined Enrollment of Aetna and Humana Includes At Least Half of the Medicare Advantage Market
(Among counties with at least 10,000 Medicare Advantage enrollees as of March 2015)
State County Total Medicare Advantage Enrollment Percent of Enrollees in Firm’s Plans
Aetna Humana Aetna-Humana
Combined
Arkansas Benton 11,447 56% 20% 76%
Arizona Mohave 15,339 54% 1% 55%
Florida Broward 151,997 55% 9% 64%
Florida Flagler 12,004 50% 3% 53%
Florida Hillsborough 94,334 48% 6% 53%
Florida Palm Beach 106,636 62% 7% 69%
Florida Pasco 60,336 47% 2% 50%
Florida Volusia 58,661 55% 1% 56%
Iowa Polk 12,103 22% 55% 77%
Illinois Winnebago 15,413 35% 41% 76%
Kansas Johnson 22,473 40% 45% 86%
Kansas Sedgwick 14,426 40% 57% 98%
Kentucky Fayette 13,038 69% 2% 72%
Kentucky Jefferson 39,769 56% 3% 58%
Louisiana East Baton Rouge 29,042 71% 1% 73%
Louisiana Jefferson 44,677 59% 1% 60%
Louisiana Livingston 10,020 78% 0% 78%
Louisiana St. Tammany 21,344 61% 3% 63%
Missouri Greene 22,276 25% 36% 61%
Missouri Jackson 40,693 45% 35% 80%
North Carolina Gaston 13,517 39% 12% 51%
Ohio Butler 23,968 31% 23% 54%
Ohio Clark 13,177 19% 45% 64%
Ohio Clermont 14,573 35% 17% 53%
Ohio Delaware 10,438 35% 31% 66%
Ohio Franklin 70,369 35% 22% 57%
Ohio Hamilton 50,269 36% 19% 55%
Ohio Lorain 18,927 30% 27% 57%
Pennsylvania Lancaster 36,445 9% 47% 56%
South Carolina Anderson 12,271 77% 1% 78%
South Carolina Greenville 25,729 63% 1% 64%
South Carolina Spartanburg 20,307 56% 0% 56%
Tennessee Blount 11,226 68% 1% 69%
Tennessee Knox 32,821 71% 0% 71%
Texas Travis 28,423 52% 12% 64%
Texas Williamson 16,731 41% 13% 54%
Virginia Chesterfield 10,201 58% 5% 63%
Virginia Henrico 10,226 60% 4% 64%
West Virginia Kanawha 13,620 64% 18% 82%
SOURCE: Kaiser Family Foundation analysis of the CMS Medicare Advantage enrollment files for March 2015.
Table 3:  Medicare Advantage Market Share of the Five Firms in the 50 Counties with the Most Medicare Advantage Enrollees, 2015
State County Total Medicare Advantage Enrollment Percent of Enrollees in Firm’s Plans
Aetna Anthem Cigna Humana United-Healthcare All Others
Arizona Maricopa 251,368 1% 2% 16% 13% 30% 38%
Arizona Pima 87,014 1% 12% 0% 8% 53% 26%
California Alameda 91,850 0% 0% 0% 3% 6% 90%
California Contra Costa 80,756 0% 0% 0% 8% 3% 89%
California Los Angeles 579,072 1% 6% 0% 1% 15% 77%
California Orange 209,338 1% 7% 0% 2% 21% 69%
California Riverside 166,613 3% 2% 0% 7% 19% 70%
California Sacramento 101,377 0% 0% 0% 1% 14% 84%
California San Bernardino 134,393 3% 4% 0% 3% 19% 71%
California San Diego 195,134 2% 2% 0% 2% 32% 62%
California Santa Clara 93,191 1% 4% 0% 1% 8% 86%
Florida Broward 151,997 9% 0% 0% 55% 13% 23%
Florida Hillsborough 94,334 6% 1% 0% 48% 20% 25%
Florida Miami-Dade 260,533 7% 7% 17% 28% 24% 17%
Florida Orange 69,567 1% 1% 0% 39% 14% 45%
Florida Palm Beach 106,636 7% 0% 0% 62% 17% 14%
Florida Pasco 60,336 2% 0% 0% 47% 18% 32%
Florida Pinellas 101,445 4% 1% 0% 39% 25% 32%
Florida Polk 62,279 9% 6% 0% 33% 25% 27%
Florida Volusia 58,661 1% 0% 0% 55% 14% 30%
Hawaii Honolulu 78,819 0% 0% 0% 9% 22% 69%
Illinois Cook 132,940 4% 0% 11% 32% 29% 24%
Massachusetts Middlesex 54,970 0% 0% 0% 0% 18% 81%
Michigan Oakland 67,658 1% 0% 0% 8% 1% 90%
Michigan Wayne 98,745 1% 0% 0% 8% 0% 91%
Minnesota Hennepin 95,706 0% 0% 0% 5% 0% 94%
Missouri St. Louis 67,505 27% 2% 0% 4% 35% 32%
Nevada Clark 112,875 5% 5% 0% 38% 51% 1%
New Mexico Bernalillo 54,649 0% 2% 0% 6% 9% 82%
New York Bronx 99,732 2% 8% 0% 0% 11% 79%
New York Erie 104,339 2% 0% 0% 0% 4% 94%
New York Kings 136,552 4% 9% 0% 0% 18% 69%
New York Monroe 89,841 7% 0% 0% 0% 10% 84%
New York Nassau 57,586 4% 35% 0% 1% 13% 47%
New York New York 89,688 3% 8% 0% 0% 23% 65%
New York Queens 139,785 4% 14% 0% 0% 26% 56%
New York Suffolk 55,316 4% 55% 0% 1% 14% 27%
Ohio Cuyahoga 89,639 18% 33% 0% 23% 12% 14%
Ohio Franklin 70,369 22% 10% 0% 35% 9% 24%
Oregon Multnomah 63,484 0% 0% 0% 2% 14% 84%
Pennsylvania Allegheny 154,168 17% 0% 0% 1% 1% 81%
Pennsylvania Philadelphia 105,432 11% 0% 41% 2% 1% 45%
Pennsylvania Westmoreland 55,381 24% 0% 0% 1% 0% 75%
Texas Bexar 104,465 10% 4% 3% 27% 50% 7%
Texas Dallas 86,485 12% 0% 3% 15% 54% 15%
Texas El Paso 54,977 6% 12% 5% 21% 36% 20%
Texas Harris 181,054 10% 8% 17% 9% 14% 42%
Texas Tarrant 92,344 8% 4% 2% 9% 65% 12%
Washington King 96,623 1% 1% 0% 7% 30% 62%
Wisconsin Milwaukee 59,870 0% 2% 0% 14% 73% 11%

SOURCE:  Kaiser Family Foundation analysis of CMS Medicare Advantage enrollment files for March 2015.

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