We study insurers' use of prescription drug formularies to screen consumers in the ACA Health Insurance Exchanges. We begin by showing that Exchange risk adjustment and reinsurance succeed in neutralizing selection incentives for most, but not all, consumer types. A minority of consumers,...

Risk adjustment of payments to health plans is fundamental to regulated competition among private insurers, which serves as the basis of national health policy in many countries. To date, estimation and evaluation of a risk adjustment model has been a two-step process. In a first step, the...

The Affordable Care Act Marketplaces were introduced in 2014 as part of a reform of the U.S. individual health insurance market. While the individual market represents a small slice of the U.S. population, it has historically been the market segment with the lowest rates of take-up and greatest...

In order to encourage entry and lower prices, most regulated markets for health insurance include policies that seek to reduce the uncertainty faced by insurers. In addition to risk adjustment of premiums paid to plans, the Health Insurance Marketplaces established by the Affordable Care Act...

Medicaid, the government program for providing health insurance to low-income and disabled Americans, is the largest health insurer in the United States with more than 73 million enrollees. It is also the sector of the U.S. public health insurance system that relies most heavily on the tools of...

Exploiting random assignment of Medicaid beneficiaries to managed care plans, we identify plan-specific effects on healthcare utilization. Auto-assignment to the lowest-spending plan generates 30% lower spending than if the same enrollee were assigned to the highest-spending plan, despite...

Public health insurance benefits in the U.S. are increasingly provided by private firms, despite mixed evidence on welfare effects. We investigate the impact of privatization in Medicaid by exploiting the staggered introduction of county-level mandates in Texas that required disabled...

Two of the three elements of the ACA's “premium stabilization program,” reinsurance and risk corridors, are set to expire in 2017, leaving risk adjustment alone to protect plans against risk of high-cost cases. This paper considers potential modifications of the HHS risk adjustment...

We leverage two unique natural experiments to show that, in public drug insurance for the low-income elderly in the U.S., defaults have large and persistent effects on plan enrollment and beneficiary drug utilization. We estimate that when a beneficiary's default is exogenously changed from one...

Health insurance markets face two forms of adverse selection problems. On the demand side, adverse selection leads to plan price distortions and inefficient sorting of consumers across health plans. On the supply side, adverse selection creates incentives for plans to inefficiently distort...