The termination of cost-sharing reduction subsidy payments to insurers in 2017 by the administration of President Donald Trump resulted in a proliferation of Marketplace plans having zero-dollar premiums in 2018 and 2019. While it is known that lower premiums increase Marketplace enrollment, it is not clear whether a zero-price effect exists in which enrollment spikes when health insurance is free. We examined whether such an effect exists and found that increased availability of zero-dollar premium plans would have caused a 14.1 percent enrollment increase among lower-income Marketplace enrollees in 2019. If zero-dollar premium plans had not been available in 2019, our simulation results suggest that enrollment in the federally facilitated Marketplace would have decreased by roughly 200,000 enrollees. When we accounted for this zero-price effect, we found that variation in premiums above zero dollars was not associated with enrollment changes. These results suggest that efforts to insure lower-income populations should focus on making health insurance free to potential enrollees, instead of simply reducing premiums. However, increased enrollment in zero-dollar premium plans could result in increased cost sharing among Marketplace enrollees and increased federal outlays for Advance Premium Tax Credits.
Keywords: Affordable Care Act; Cost sharing; Enrollment; Health insurance exchanges; Health policy; Open enrollment; Premiums; Private health insurance; Qualified health plans; payment.