Which states saw the largest percentage growth in Marketplace enrollment from 2020 to 2025 and why did expansion status matter?

1. Which states saw the biggest percentage increases — the headline list

Multiple public summaries flag six states where Marketplace enrollment has more than tripled between 2020 and 2025 — Georgia, Louisiana, Mississippi, Tennessee, Texas, and West Virginia — a finding cited by industry reporting that draws on KFF and CMS figures ^[1]; KFF’s broader state data and trackers also document that nearly all states saw substantial gains and that about 20 states doubled enrollments since 2020 ^{[5] [6]}.

2. Why Medicaid expansion status mattered — mechanics and magnitude

Non‑expansion states experienced far faster Marketplace growth: KFF finds Marketplace enrollment rose roughly 188% in states that had not expanded Medicaid versus about 65% in expansion states from 2020–2025, a stark divergence that points to structural differences in who is eligible for Medicaid versus Marketplace subsidies ^{[2] [7]}.

3. How expansion (or lack of it) produces that result — the practical pathway

In expansion states, many low‑income adults fall into Medicaid and therefore are not counted as Marketplace enrollees, whereas in non‑expansion states people with incomes at or just above poverty often must use the Marketplace to get subsidized coverage — a dynamic KFF and Georgetown’s Center for Children and Families describe as a key reason parents and low‑income adults in non‑expansion states show larger Marketplace shares and faster growth ^{[3] [8]}.

4. Other powerful forces: subsidies, platform, and state program quirks

Enhanced premium tax credits enacted in ARPA and extended by the Inflation Reduction Act through 2025 were the principal national driver making Marketplace plans affordable and fueling enrollment surges ^{[2] [4]}; KFF and CMS also note that states using the federal HealthCare.gov platform tended to register the fastest Marketplace growth, and that some states with alternative programs — for example New York and Oregon with Basic Health Plans or section 1332 waivers — actually saw their Marketplace totals shrink because low‑income consumers are routed into those other coverage streams ^{[9] [2] [3]}.

5. Politics, geography, and the risk of simplistic narratives

KFF highlights a geographic and political concentration of growth — 31 states carried by President Trump in 2024 accounted for roughly 88% of Marketplace gains — but that pattern overlaps with the policy explanation: many of those states were non‑expansion, had high uninsured rates pre‑2020, and therefore had more room for Marketplace growth once subsidies increased ^{[2] [10]}. This dual framing means political headlines can exaggerate narrative causation unless paired with the policy mechanics documented by KFF and others ^[3].

6. Caveats, data limits, and why this matters going forward

Public analyses and CMS files document the broad trends and list top states, but precise state‑by‑state percent changes and enrollment drivers are tied to differing reporting windows (state‑by‑state SBM vs. FFM reporting dates) and to program nuances like Basic Health Plans and expansion timing, so interpretations should rely on the underlying KFF and CMS datasets rather than single headlines ^{[11] [6] [9]}; critically, the enhanced subsidies that powered much of the growth are set to expire absent Congressional action, a policy cliff that would alter enrollment trajectories and equity between expansion and non‑expansion states ^{[2] [12]}.