The Biden administration announced last week that enrollment in ACA marketplace plans had reached an all-time high of 13.6 million* as of December 15, with a month still to go in the open enrollment period (OEP) for 2022 in most states.

That’s an increase of about 2 million (17%) over enrollment as of the same date last year, according to Charles Gaba’s estimate, and well above the previous high of 12.7 million recorded as of the end of open enrollment for 2016, which lasted until January 31 in most states. When OEP ends this coming January, enrollment in marketplace plans will exceed 14 million.

In the 33 states using the federal exchange, HealthCare.gov (for which the federal government provides more detailed statistics than in the 18 state-based exchanges), almost all enrollees (92%) received premium tax credits (subsidies) to help pay for coverage – including 400,000 who would not have qualified for subsidies prior to passage in March of this year of the American Rescue Plan (ARP). That bill not only increased premium subsidies at every income level through 2022, but also removed the previous income cap on subsidies, which was 400% of the federal poverty level (FPL) ($51,520 per year for an individual and $106,000 for a family of four). In 2022, no enrollee who lacks access to other affordable insurance pays more than 8.5% of income for a benchmark Silver plan (the second cheapest Silver plan in each area), and most pay far less.

The enrollment increase is tribute to the huge boost in affordability created by the ARP subsidies. A benchmark Silver plan with strong Cost Sharing Reduction (CSR, attached to Silver plans for low-income enrollees) is now free at incomes up to 150%FPL ($19,320 for an individual, $39,750 for a family of four in 2022) and costs no more than 2% of income ($43/month for an individual) at incomes up to 200% FPL. The percentage of income required for the benchmark Silver plan  was reduced at higher incomes as well.  The ARP also provided free high-CSR Silver coverage to anyone who received any unemployment insurance income in 2021.

The enrollment gains during OEP build on the enrollment surge triggered by the emergency special enrollment period (SEP) opened by the Biden administration on February 15 of this year, which ran through August 15 in the 33 states using HealthCare.gov, and for varying periods in the 15 states that ran their own exchanges in 2021. (There are now 18 state-based exchanges, as Kentucky, Maine and New Mexico launched new ones for 2022.)

The ARP subsidies came online in April (or May in a few state marketplaces). From February to August, 2.8 million people enrolled during the SEP, and total enrollment increased by 900,000 on net from February to August (as people also disenrolled every month, and many enrollees doubtless regained employer-sponsored coverage during a period of rapid job growth).

In addition, once the ARP subsidy increases went into effect, 8 million existing enrollees saw their premiums reduced by an average of 50%, from $134 to $67 per month. Enrollees’ premiums in 2022 should be similar to those of the SEP.

Enrollment increases during open enrollment – as during the SEP and the OEP for 2021 – were heavily concentrated in states that have not enacted the ACA expansion of Medicaid eligibility. There were 14 such states during most of the SEP and 12 during the (still current) OEP, as Oklahoma belatedly enacted the Medicaid expansion starting in July of this year, and Missouri in October.

In non-expansion states, eligibility for ACA premium subsidies begins at 100% FPL, while in states that have enacted the expansion, marketplace subsidy eligibility begins at 138% FPL, and Medicaid is available below that threshold. In non-expansion states, the marketplace is the only route to coverage for most low-income adults, and those who report incomes below 100% FPL mostly get no help at all – they are in the notorious coverage gap. In those states, about 40% of marketplace enrollees have incomes below 138% FPL – that is, they would be enrolled in Medicaid if their states enacted the expansion.

During OEP, these 12 non-expansion states account for 81% of the enrollment gains in the 33 HealthCare.gov states, and about two-thirds of enrollment gains in all states. The table below also shows gains over a two-year period, encompassing the effects of the COVID-19 pandemic.

In the 39 states that have enacted the ACA Medicaid expansion (21 on HealthCare.gov and 18 running their own exchanges), far fewer enrollees are eligible for free Silver coverage. In expansion states, eligibility for marketplace subsidies begins at an income of 138% FPL, as people below that threshold are eligible for Medicaid. Nevertheless, enrollment growth in non-expansion states during the current OEP is substantial, increasing by about 755,000 year-over-year, or 13%.

The marketplace has been a bulwark against uninsurance during the pandemic, among low-income people especially and in the non-expansion states in particular. As shown in the chart above, enrollment in these 11 states increased by 1.8 million from Dec. 15, 2019 to Dec. 15, 2021 – a 37% increase. For all states, the two-year increase is in the neighborhood of 25% and will approach 3 million (from 11.4 million in OEP for 2020 to above 14 million when OEP for 2022 ends in January). That’s in addition to an increase of more than 12 million in Medicaid enrollment during the pandemic.

While millions of Americans lost jobs when the pandemic struck, and millions fewer are employed today than in February 2020, the uninsured rate did not increase during 2020, according to government surveys, and may even prove to have downticked during 2021 or 2022 when the data comes in.

While the government has not yet published detailed statistics as to who has enrolled during the current OEP, they did do so in the final enrollment report for the emergency SEP. During the emergency SEP, out of 2.8 million new enrollees, 2.1 million were in the 33 HealthCare.gov states. In those states, 41% of enrollees obtained Silver plans with the highest level of CSR, which means that they had incomes under 150% FPL (or received unemployment income) and so received free coverage in plans with an actuarial value of 94% – far above the norm for employer-sponsored plans.

The median deductible obtained in HealthCare.gov states was $50, which makes sense, as 54% of enrollees obtained Silver plans with strong CSR, raising the plan’s actuarial value to either 94% (at incomes up to 150% FPL) or to 87% (at incomes between 150% and 200% FPL). Two-thirds of enrollees in HealthCare.gov states paid less than $50 per month for coverage, and 37% obtained coverage for free.

At higher incomes, as noted above, 400,000 enrollees who received subsidies in HealthCare.gov states would not have been subsidy-eligible before the ARP lifted the income cap on subsidies (previously 400% FPL). The same is also doubtless true for several hundred thousand enrollees in state-based marketplaces. The SBEs account for a bit less than a third of all enrollment, but in those states, all of which have expanded Medicaid, the percentage of enrollees with income over 400% FPL is almost twice that of the HealthCare.gov states (12% versus 7% during the emergency SEP).

Marketplace subsidies are based on an estimate of future income. For low-income people in particular, who are often paid by the hour, work uncertain schedules, depend on tips, or are self-employed, income can be difficult to project. The desire to be insured during the pandemic may have spurred some applicants to make sure their estimates cleared the 100% FPL threshold. (Enrollment assisters and brokers can help applicants deploy every resource to meet this goal.)

For OEP 2022, the Biden administration raised funding for nonprofit enrollment assistance in HealthCare.gov states to record levels, enough to train and certify more than 1,500 enrollment navigators. This past spring, in compliance with a court order, the exchanges stopped requiring low-income applicants who estimated income  over 100% FPL to provide documentation if the government’s “trusted sources” of information indicated an  income below the threshold.

Comparatively weak enrollment growth in Wisconsin may support the hypothesis that under pressure of the pandemic, some enrollees in other non-expansion states are climbing out of the coverage gap. Alone among non-expansion states, Wisconsin has no coverage gap, as the state provides Medicaid to adults with incomes up to 100% FPL (rather than up to the 138% FPL threshold required by the ACA Medicaid expansion, which offers enhanced federal funding to participating states). In Wisconsin, those whose income falls below the 100% FPL marketplace eligibility threshold have access to free coverage. Wisconsin is the only non-expansion state that did not experience double-digit enrollment growth in OEP 2022 or from 2020-2022.

The American Rescue Plan was conceived as emergency pandemic relief, and its increased subsidies run only through 2022. President Biden’s Build Back Better bill, which passed in the House of Representatives but is currently stalled in the Senate, would extend the ARP subsidies through 2025 or possibly further.

The large increase in enrollment this year should add pressure on Congress to extend the improved subsidies into future years. Consumer response to the increased subsidies has proved immediate and dramatic. The ARP subsidy boosts brought the Affordable Care Act much closer than previously to living up to the promise of “affordable” care expressed in its name. Going backwards on that promise should not be seen as a politically viable or ethical path.

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* Another million people are enrolled in Basic Health Programs established under the ACA by Minnesota and New York – low-cost, Medicaid-like programs for state residents with incomes under 200% FPL. Enrollment in these programs is on track to increase by 13% this year, according to Charles Gaba’s estimate.

** HealthCare.gov all-state totals are for the 33 states using the federal exchange this year. Source: Charles Gaba, OE snapshots as of mid-December, 2021-22, 2020-2021; see also CMS end-of-OEP snapshots for 2020, 2021, 2022

Andrew Sprung is a freelance writer who blogs about politics and healthcare policy at xpostfactoid. His articles about the Affordable Care Act have appeared in publications including The American Prospect, Health Affairs, The Atlantic, and The New Republic. He is the winner of the National Institute of Health Care Management’s 2016 Digital Media Award. He holds a Ph.D. in English literature from the University of Rochester.