Submission history

Published online: July 6, 2026

Published in issue: July 14, 2026

Acknowledgments

We are grateful to Rajan Topiwala for fact-checking and Sean Dunbar, Caroline Hanson, Tamara Hayford, Alexandra Minicozzi, Rob Stewart, Carolyn Ugolino, Chapin White, and three anonymous reviewers for helpful comments. This article has not been subject to the Congressional Budget Office’s regular review and editing process. The views expressed here are those of the authors and should not be interpreted as those of the Congressional Budget Office.

Author contributions

N.H. and B.H. designed research; performed research; contributed new reagents/analytic tools; analyzed data; and wrote the paper.

Competing interests

The authors declare no competing interest.

Notes

This article is a PNAS Direct Submission. A.C. is a guest editor invited by the Editorial Board.

*

All proposals are estimated relative to the agency’s baseline projections for coverage and budgetary outcomes over a 10-year period.

†

Nongroup insurance is private insurance that is purchased through the health insurance marketplaces established under the Affordable Care Act (ACA) or outside them, through brokers or directly from insurers.

‡

For more information about HISIM2, see (

106,

107).

§

In reviewing this literature, CBO makes no judgement on whether the changes in take-up rates induced by policies are justified.

¶

The premium tax credit is an advanceable and refundable credit that reduces enrollees’ out-of-pocket costs for the premiums they pay for health insurance obtained through the marketplaces.

#

In the context of HISIM2, households refer to “health insurance units,” (HIUs) which are defined in the model as groups of people who live together and would be eligible for coverage under the same employment-based family plan. Asingle person is his or her own HIU. Otherwise, an HIU is the set of individuals who could be covered by a family plan—that is, a plan that covers an employee and his or her dependents—if an employer offered that plan.

‖

For details on the specification of the utility function in HISIM2, see (

107).

For marketplace coverage, federal subsidies come in the form of the premium tax credit (PTC)—a tax credit that eligible people can use to lower the out-of-pocket cost of their monthly premiums for health insurance coverage purchased through the ACA marketplaces. Some marketplace enrollees have access to “zero-premium plans” for which the PTC fully covers the premium.

††

Between March 2020 and March 2023, all states provided continuous eligibility to enrollees in Medicaid and Medicaid expansions of CHIP as a condition to receive additional federal Medicaid funding. This provision allowed people to remain enrolled during that period regardless of changes in their eligibility.

‡‡

Under the ACA, marketplace enrollees with income below 250 percent of the FPL are eligible but not required to enroll in plans with reduced cost-sharing.

§§

In addition to PTCs, marketplace enrollees may also be eligible for cost-sharing reductions (CSRs), which reduce patients out-of-pocket costs for health care but are available only in silver-tier plans. In 2017, federal payments to insurers to fund CSRs were discontinued. Insurers in most states recouped this lost funding by increasing premiums for silver plans; this practice is known as “silver loading.” Because PTCs under the ACA are tied to the price of a benchmark silver plan, silver loading increased the dollar value of PTCs. For many low-income enrollees, the larger PTCs fully covered the premiums of less expensive plans.

¶¶

Under the ACA, states have the option to run a state-based marketplace that manages eligibility determinations, applications, and enrollment. For all other states, these functions are managed through the “federally facilitated marketplace” run by the Department of Health and Human Services.

##

Calculation: Numerator from (

108) and denominator from (

109).