In this paper, we explore Affordable Care Act (ACA) Marketplace premiums at the state and rating region levels, focusing on the changes between 2020 and 2021. In 2021, the ACA Marketplaces entered their eighth year of operation and premiums have stabilized. The national average benchmark premium fell again in 2021, following decreases in both 2019 and 2020. This decline is remarkable because it contrasts with premium increases in the employer-sponsored insurance market over the same period. However, the nationwide average belies the variation in premiums both across and within states. We find that insurer participation is key to setting premium levels and influencing growth over time. State policymakers may adopt policies that directly and indirectly affect premiums and premium growth rates.
We found that the number of insurers was a strong predictor of lower premiums; markets with only one or two insurers had substantially higher premiums than markets with five or more insurers. On the other hand, the presence of a Medicaid insurer was associated with lower premiums. Similarly, regions in states that expanded Medicaid or established state-based Marketplaces had lower premiums than regions in states that had not enacted such policies. Finally, we looked at changes in participation by specific insurers in 52 rating regions in 20 states, a sample including most large urban markets. Two large national insurers, Humana and Aetna, left the market in 2017 and have not returned. In contrast, United Healthcare and Cigna have increased the number of regions in which they participate. There have been small increases in participation by Blue Cross and Blue Shield. Since 2017 Centene, a Medicaid insurer, has increased participation dramatically. Two new insurers, Oscar and Bright have also increased participation. Oscar was in three rating regions in 2017 and 21 in 2021. Bright was in no rating regions in 2017 and now participates in nine.