Insurers expect a weaker ACA risk pool in 2027, but their filings do not isolate its premium effect

The defensible answer is that the risk-pool contribution cannot yet be isolated. Peterson-KFF found a 14% medianmedianThe median is the middle value after observations are placed in order. request among 77 insurers and a 10% median medical and prescription-drug trend among filings that disclosed that measure. It also reported that insurers adjusting for the expiration of enhanced premium tax creditsenhanced premium tax creditsEnhanced premium tax credits were temporary increases in Marketplace assistance that applied from 2021 through 2025. expected the resulting risk-pool change to add roughly 4 percentage points. The analysis did not publish the number of insurers behind the latter two figures or an average risk-pool effect for all 77 insurers. https://www.healthsystemtracker.org/brief/how-much-and-why-acaacaThe Affordable Care Act is the federal law that created regulated health-insurance Marketplaces and subsidies for eligible households.-marketplacemarketplaceA Marketplace is a government-regulated service through which individuals can compare and buy health plans.-premiums-are-going-up-in-2027/

Putting 14, 10 and 4 beside one another can make them look like pieces of one bill. They are not. Medical trendMedical trendMedical trend is an insurer's forecast of growth in claims costs caused by changes in healthcare prices, service use, treatment mix and prescription-drug spending. is a forecast used inside a pricing calculation. An insurerinsurerAn insurer is a company that collects premiums and pays covered healthcare claims. can apply that trend to an earlier claims base and then make separate adjustments for changing benefits, administration, financial margins, risk adjustmentrisk adjustmentRisk adjustment transfers money among insurers so plans covering people with greater expected medical needs receive compensation. or earlier pricing errors. Peterson-KFF describes medical trend as growth in the underlying cost of medical care and prescription drugs, while its risk-pool figure applies only to insurers making that adjustment. https://www.healthsystemtracker.org/brief/how-much-and-why-aca-marketplace-premiums-are-going-up-in-2027/

Medical costs are the clearest quantified pressure, but the available filings do not reveal what share of the typical premium request comes from adverse selection.

The proposed changes range from 1% to 52%. The middle half lies between 12% and 21%, 20 insurers requested increases above 20%, and none of the 77 requested a decrease. The sample covers publicly available filings from 16 states and Washington, D.C.; Hawaii, Illinois and Texas have only partial insurer coverage in the analysis. Peterson-KFF says regulators will finalize the rates in late summer. https://www.healthsystemtracker.org/brief/how-much-and-why-aca-marketplace-premiums-are-going-up-in-2027/

This is an insurer-level distribution, not a national average of what every customer will pay. Peterson-KFF calculated each observation as an enrollment-weightedenrollment-weightedAn enrollment-weighted calculation gives more influence to products covering more people. average across one insurer's bronze, silver, gold and platinum products within a state. The calculation also differs from the change in the benchmark silver planbenchmark silver planThe benchmark silver plan is the second-lowest-cost silver plan in an area and is used to calculate premium tax credits. used to determine subsidies. https://www.healthsystemtracker.org/brief/how-much-and-why-aca-marketplace-premiums-are-going-up-in-2027/

A requested gross-premium increase also does not translate mechanically into the same increase in a subsidized household's bill. A premium tax creditpremium tax creditA premium tax credit is federal assistance that reduces what an eligible household pays for Marketplace insurance. reduces the amount an eligible enrollee pays, and its size depends partly on the local benchmark plan. Peterson-KFF reported that 87% of 2026 Marketplace plan selectors received a premium subsidysubsidyA subsidy is government assistance that lowers a person's cost., although the protection from any particular increase depends on the plan chosen and the household's eligibility. https://www.healthsystemtracker.org/brief/how-much-and-why-aca-marketplace-premiums-are-going-up-in-2027/ ; https://www.cms.gov/files/document/health-insurance-exchanges-2026-open-enrollment-report.pdf

Peterson-KFF identified growth in healthcare prices and use as the primary driver described in the filings. The median disclosed medical trend was 10%, compared with 8% in each of the previous few years. Filings cited provider contract increases, hospital and physician services, prescription drugs, labor costs and greater claims severityclaims severityClaims severity describes how complex and expensive the average claim is.. https://www.healthsystemtracker.org/brief/how-much-and-why-aca-marketplace-premiums-are-going-up-in-2027/

Those filing narratives provide examples rather than a uniform accounting system. Moda Health Plan in Oregon reported a 10.2% annualized trend and said trend and prior claims experience accounted for a significant portion of its request. ConnectiCare in Connecticut said medical inflation related to the use and cost of covered services increased claims by 9.2%. These insurer-specific figures illustrate the pressure but do not establish the contribution for the median insurer. https://www.healthsystemtracker.org/brief/how-much-and-why-aca-marketplace-premiums-are-going-up-in-2027/

Enhanced premium tax credits expired at the end of 2025. Peterson-KFF reports that insurers making an explicit adjustment for that expiration generally expect higher net premiums to reduce enrollment and leave a population with greater average medical needs. Among those insurers, the expected 2027 premium effect was roughly 4 percentage points. Some filings used larger insurer-specific assumptions, including 6.0% at Antidote Health in Texas and 4.7% at Maine Community Health Options. https://www.healthsystemtracker.org/brief/how-much-and-why-aca-marketplace-premiums-are-going-up-in-2027/

The economic logic is adverse selectionadverse selectionAdverse selection occurs when people expecting lower medical costs are more likely to leave or avoid coverage, raising the average expected cost of those insured.: people who expect little healthcare may see less value in paying a higher premium, while people expecting substantial care have a stronger reason to remain insured. The Congressional Budget Office made the same behavioral assumption when it estimated that, without an extension of the enhanced credits, gross benchmark premiums would be 4.3% higher in 2026 and 7.7% higher in 2027 than under an extension. Those CBO figures compare two policy scenarios; they are not measurements of the contribution inside the current 14% filing median. https://www.cbo.gov/system/files/2024-12/59230-ARPA.pdf

The filings still do not prove that the people leaving coverage were healthier than those remaining. They state insurers' expectations about future morbiditymorbidityMorbidity is insurance shorthand for the expected medical needs and costs of a covered population.. Establishing the effect would require outcome evidence such as changes in standardized risk scores, risk-adjustment transfers or claims per member after separating changes in medical prices and covered benefits. CMS explains that risk adjustment is intended to compensate plans enrolling people with higher healthcare costs and reduce incentives to avoid sicker members. https://www.cms.gov/marketplace/health-plans-issuers/premium-stabilization-programs

Federal data put effectuated Marketplace enrollment at an estimated 19.2 million in February 2026. KFF compared that figure with the reported 2025 high of 22.1 million and calculated a 13% decline. Because one figure is a yearly high and the other is a February count, the comparison should be read as evidence of a substantial fall from the peak, not as a matched month-to-month estimate. https://aspe.hhs.gov/reports/aca-exchange-enrollment-2026 ; https://www.kff.org/quick-insights/aca-marketplace-enrollment-is-down-by-3-million-after-big-jump-in-premium-payments/

The enrollment decline coincided with the expiration of enhanced tax credits and with federal eligibility and program-integrity changes. CMS says its actions ended subsidies or coverage for nearly 1.5 million people on the HealthCare.gov platform who were found ineligible for financial assistance or enrolled without authorization. The 2025 Marketplace Integrity and Affordability Final Rule also strengthened income verification, changed automatic re-enrollment and required a temporary 5-dollar monthly payment from certain people automatically re-enrolled in otherwise zero-premium coverage. https://www.cms.gov/newsroom/fact-sheets/cms-actions-protect-consumers-strengthen-exchange-program-integrity ; https://www.cms.gov/newsroom/fact-sheets/2025-marketplace-integrity-and-affordability-final-rule

Those simultaneous changes prevent a clean causal reading of the national enrollment total. Higher consumer payments may have caused some people to leave, while eligibility enforcement and re-enrollment changes may have removed other records. A national headcount alone does not reveal either group's health status. https://www.kff.org/quick-insights/aca-marketplace-enrollment-is-down-by-3-million-after-big-jump-in-premium-payments/ ; https://aspe.hhs.gov/reports/aca-exchange-enrollment-2026 ; https://www.cms.gov/newsroom/fact-sheets/cms-actions-protect-consumers-strengthen-exchange-program-integrity

Finalized rates will show how regulators changed the requests, but they still will not by themselves prove why the risk poolrisk poolA risk pool is the group of insured people whose expected healthcare costs are combined when coverage is priced. changed. The stronger test is to connect enrollment losses with later measures of expected and actual medical cost. CMS publishes risk-adjustment information designed to compare enrollee risk across plans, while subsequent claims can show spending per member. https://www.cms.gov/marketplace/health-plans-issuers/premium-stabilization-programs

If measured risk and price-adjusted claims remain broadly stable while hospital, physician and drug costs rise, the medical-cost explanation would strengthen. If comparable risk measures rise most in markets with larger enrollment losses, the adverse-selection explanation would gain support. If enrollment removals are concentrated among ineligible or unauthorized records without a corresponding rise in measured risk, program cleanup would explain more of the contraction. These are research tests, not conclusions supported by the preliminary filings.

For now, the filings show that insurers expect adverse selection. They do not measure how much adverse selection has occurred.