A new KFF analysis finds that there were 44 million people enrolled in health coverage through the Affordable Care Act's Marketplaces and its expansion of the Medicaid program in 2024. That represents about 1 in every 6 people under age 65, or 16.4%.

There was significant variation in ACA enrollment across states, ranging from about 1 in 4 nonelderly people in Louisiana, Oregon, Florida, and New York to fewer than 1 in 10 in Tennessee, Alabama, Wyoming, Kansas, and Wisconsin, according to the analysis.

With the exception of Florida, the states with the largest ACA-related enrollment as a share of population had adopted the Medicaid expansion, while all five states with the lowest share of enrollment were non-expansion states. (The data includes enrollment in the Basic Health Program, an option offered by some states under the ACA to provide coverage for low-income residents who would otherwise be eligible to obtain coverage through the Marketplace. There were 1.3 million people enrolled in this option in 2024.)

The new analysis helps illustrate how many people could potentially be affected by the anticipated policy debates in Congress, including whether to allow enhanced ACA Marketplace subsidies to expire this year, whether to reduce the federal share of Medicaid expansion funding, or whether to enact deeper spending cuts to ACA subsidies and Medicaid to help pay for expected tax cuts.

From 2020 to 2024, total enrollment in ACA programs (Medicaid, Marketplace, and Basic Health Plan) increased by nearly 60%, with the largest increase among Marketplace enrollees, helping to drive the uninsured rate down to historic lows. The number of Marketplace enrollees increased by 10 million people nationally, almost doubling, over the period, and the number of Medicaid expansion enrollees increased by 6.2 million people. States with the largest increases in enrollment, in percentage terms, included Missouri (243%), Oklahoma (227%), Texas (212%), Mississippi (190%), North Carolina (185%) and Georgia (186%).

Growth in Marketplace enrollment over the period can be largely attributed to the temporary enhanced subsidies that were made available in 2021, which were extended through 2025. Marketplace enrollment climbed to a new record high in 2025, with nearly 24 million people signing up for plans during the current enrollment period. Marketplace enrollment was 21.4 million in 2024.

Medicaid expansion enrollment increased due to more states implementing expansion (seven states-Idaho, Missouri, Nebraska, North Carolina, Oklahoma, South Dakota, and Utah-implemented Medicaid expansion during or after 2020) and because of the pause in disenrollments from the pandemic-era continuous enrollment provision. Medicaid expansion enrollment totaled 21.3 million people in 2024. Even with the unwinding of the continuous enrollment provision that was still in play through March 2024, overall enrollment in Medicaid expansion is higher than in 2020.