TDFP Exclusive: 3 Insurers Hold 80%+ of Obamacare Markets in 49 States, GAO Finds

In 49 states, the three largest insurers held at least 80% of enrollment in the Affordable Care Act exchanges in 2024, according to a new report from the Government Accountability Office, the audit arm of Congress. GAO counts the District of Columbia as a state, so that is 49 of 51.

The report, released Oct. 16, is the seventh in a series the Affordable Care Act requires GAO to produce on competition in health insurance. It found that private insurance markets are generally more concentrated than they were in 2011, though the markets where people buy their own coverage have loosened somewhat in recent years.

GAO warns that concentration can cost consumers. "A concentrated health insurance market may indicate less issuer competition and could affect consumers' choices of issuers and the premiums they pay for insurance," the report's summary says.

What GAO Found in the Exchanges

GAO treats a market as concentrated when "three or fewer issuers held at least 80 percent of the market share of enrollment."

By that test, the exchanges, also known as the Obamacare marketplaces, became more concentrated from 2015 through 2020. The number of concentrated states rose from 47 in 2015 to all 51 in 2020, then fell to 49 in 2024.

In the typical state, the three largest insurers held 94% of exchange enrollment in 2024, and the single largest held 53%. The median number of insurers per state was six, up from a low of two in 2018. Only one state had a single insurer holding 80% or more, down from 20 states in 2018.

For the exchanges, GAO measured market share across each state's rating areas, the regions insurers use to set premiums, and averaged them, weighting by enrollment. Measured statewide instead, GAO's published state data show the top three insurers held 80% or more in 35 states in 2024. In 14 states, the data list only two or three insurers with any exchange enrollment.

The exchanges now carry nearly the whole individual market. About 21.9 million of the 23.4 million people in individual plans enrolled through an exchange in 2024. Exchange enrollment more than doubled from about 9 million in 2015, according to the report.

The Wider Market

Concentration also rose in employer coverage. In the small-group market, sold to small employers, the number of concentrated states climbed from 36 in 2011 to 47 in 2024. The number of states where a single insurer held at least 80% grew from three to 16.

In the large-group market, the biggest with about 39.3 million enrollees, concentrated states rose from 40 to 45. States where one insurer held 80% or more more than doubled, from six to 13.

The overall individual market went the other way after peaking in 2019. Concentrated states fell from 47 that year to 36 in 2024. The median number of insurers in that market dropped from 30 in 2011 to nine.

Why It Matters for Premiums and Choice

GAO points to research that "found strong evidence that concentration in health insurance markets is associated with higher consumer premiums." Some studies find concentration can cut insurers' costs, the report says, but "these savings may not be passed on to consumers as lower premiums."

GAO says concentration often comes from mergers and acquisitions, from insurers leaving a market, or from big insurers taking share from smaller ones. New insurers can struggle to break in because, without many enrollees, they "may have greater challenges negotiating discounts with health care providers."

GAO notes that insurers entered the exchanges as enrollment rose during and after the pandemic. Enrollment grew after the American Rescue Plan Act of 2021 temporarily expanded premium tax credits. Those enhanced subsidies "were not extended for 2026," the report notes. The data run only through 2024, so the report does not show how the 2026 market has changed.

What HHS Said

The report makes no recommendations. GAO sent a draft to the Department of Health and Human Services, which oversees the Centers for Medicare & Medicaid Services. According to the report, "The department provided technical comments, which we incorporated as appropriate." GAO printed no other HHS response.

GAO based its findings on enrollment data insurers report to CMS, plus state and CMS exchange data. It combined insurers that share a parent company. The data cover fully insured plans only, not the self-funded plans many large employers use.

Hold Everyone Accountable.

Sources: U.S. Government Accountability Office, "Private Health Insurance: Market Concentration in 2024 Was Generally Higher Than in 2011," GAO-27-108927 (Oct. 16, 2026): https://www.gao.gov/products/gao-27-108927 ; full report PDF: https://www.gao.gov/assets/gao-27-108927.pdf ; GAO interactive graphic and state-level data: https://files.gao.gov/multimedia/gao-27-108927/interactive/index.html