Coverage Retention and Plan Switching Following Switches From a Zero- to a Positive-Premium Plan.

Importance: Millions of lower-income Health Insurance Marketplace enrollees were defaulted from zero-premium to positive-premium health plans in 2022, 2023, and 2024. This turnover in zero-premium plans may cause coverage losses by creating administrative burdens that complicate enrollees' ability to maintain coverage. Objective: To determine how turnover affected Marketplace reenrollment. Design, Setting, and Participants: This cross-sectional study used log-linear fixed-effects models including counties in 29 states that used the HealthCare.gov platform from 2022 through 2024. Exposure: HealthCare.gov enrollees living in a county that experienced turnover that year. Main Outcomes and Measures: County-year-level counts of overall reenrollment, automatic and active enrollment, and active reenrollment split by whether enrollees stayed with or switched from their previous plan. We controlled for premium affordability, insurer competition, other county characteristics, and state-by-year policy changes. Results: The sample consisted of 2159 counties representing roughly 10 million HealthCare.gov enrollees annually in 29 states that used the HealthCare.gov platform from 2022 through 2024. The share of enrollees living in counties exposed to turnover increased from 10.3% to 93.9% from 2021 to 2022 as the American Rescue Plan Act subsidies were implemented. These increases have persisted into 2024. Turnover across insurers was associated with a 7.0% (95% CI, -12.7 to -1.3) decrease in automatic reenrollment. Any turnover was not associated with changes in active enrollment, though it was associated with a 13.4% decrease (95% CI, -17.7 to -9.1) in enrollees choosing to stay with their previous, default plan and a roughly equivalent 15.0% increase (95% CI, 11.5-18.5) in enrollees choosing to switch plans. Conclusions: Turnover affects coverage losses by decreasing automatic, passive reenrollment among lower-income enrollees that may not realize they need to start paying premiums to retain coverage that previously did not have a premium. Turnover also nudges returning enrollees to select new plans rather than selecting their previous plans. This likely increases insurer price competition but also may create hassles for enrollees. These findings suggest that coverage losses from turnover in 2026 among lower-income Marketplace enrollees may be particularly large if enhanced subsidies from the Inflation Reduction Act expire.