Efficient Subsidy Targeting in the Health Insurance Marketplaces

Enrollment in the Health Insurance Marketplaces created by the Affordable Care Act reached an all-time high of approximately 25 million Americans in 2025, roughly doubling since enhanced premium tax credit subsidies were made available in 2021. The scheduled expiration of enhanced subsidies in 2026 is estimated to leave over seven million Americans without health insurance coverage. Ten states have created supplemental Marketplace subsidies, yet little attention has been paid to how to best structure these subsidies to maximize coverage. Using administrative enrollment data from Maryland's Marketplace, we estimate demand for Marketplace coverage. Then, using estimated parameters and varying budget constraints, we simulate how to optimally allocate supplemental state premium subsidies to mitigate coverage losses from enhanced premium subsidy expiration. We find that premium sensitivity is greatest among enrollees with incomes below 200 percent of the federal poverty level, where the marginal effect of an additional ten dollars in monthly subsidies on the probability of coverage is approximately 6.5 percentage points, and decreases to roughly 2.5 percentage points above 200 percent FPL. Simulation results indicate that each 10 million dollars in annual state subsidies could retain roughly 5,000 enrollees, though the cost-effectiveness of these subsidies falls considerably once all enrollees below 200 percent of the federal poverty level are fully subsidized. We conclude that states are well positioned to mitigate, but not stop, coverage losses from expanded premium tax credit subsidy expiration.