The Association of the 340B Program with Affordable Care Act (ACA) Premiums: A Longitudinal Analysis from 2018 to 2022.

We tested whether the 340B program impacts Affordable Care Act (ACA) premiums. Data from 2018 to 2022 was used to establish a baseline for silver benchmark premiums and other key measures, including: the number of active 340B sites per 10,000 people in a county (Hospital Site Density, or HSD), ACA benchmark plan premiums for every county, and measures likely to influence insurance premiums including per capita income, unemployment, and hospital market power. We used a multivariate fixed effects regression that included state and year effects, the explanatory variables, and the county-level HSD for each year. The impact of 340B on ACA premiums was illustrated using 2022 data. We estimate that a 1-unit change in 340B HSD was associated with a 1.1% (95% CI 0.73-1.15) change in the benchmark ACA premium. In 2022, the mean county 340B HSD was 1.63, and the mean Silver Benchmark Plan monthly premium was $500. After adjusting for per capita income, hospital concentration index, and other factors, the mean 340B HSD accounted for 1.8% (95% CI: 1.3-2.1) of the average Silver Benchmark Plan monthly premium, or $8.90 (95% CI $6.50-$10.25) per month, implying a cost in additional subsidies of over $106 per year per subsidized ACA enrollee. The results support that the 340B program is associated with a financially meaningful component of ACA premiums.