A Prescription for Drug Formulary Evaluation: An Application of Price Indexes

Screening in Contract Design: Evidence from the ACA Health Insurance Exchanges

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, identifiable by demand for particular classes of prescription drugs, are predictably unprofitable. We then show that contract features relating to these drugs are distorted in a manner consistent with multidimensional screening. The empirical findings support a long theoretical literature examining how insurance contracts offered in equilibrium can fail to optimally trade off risk protection and moral hazard.

Medical service provider networks

In many countries, health insurers or health plans choose to contract either with any willing providers or with preferred providers. We compare these mechanisms when two medical services are imperfect substitutes in demand and are supplied by two different firms. In both cases, the reimbursement is higher when patients select the in-network provider(s). We show that these mechanisms yield lower prices, lower providers' and insurer's profits, and lower expense than in the uniform-reimbursement case. Whatever the degree of product differentiation, a not-for-profit insurer should prefer selective contracting and select a reimbursement such that the out-of-pocket expense is null. Although all providers join the network under any-willing-provider contracting in the absence of third-party payment, an asymmetric equilibrium may exist when this billing arrangement is implemented.

A Welfare Measure of "Offset Effects" in Health Insurance

Changing health insurance coverage for one service may affect use of other insured services. When improving coverage for one service reduces use of another, the savings are referred to as "offset effects." For example, costs of better coverage for prescription drugs may be partly "offset" by reductions in hospital costs. Offset effects have welfare implications but it has not been clear how to value these impacts in design of health insurance. We show that plan-paid - rather than total -- spending is the right welfare measure of the offset effect, and go on to develop a "sufficient statistic" for evaluating the welfare effects of change in coverage in the presence of multiple goods. We derive a simple rule for when a coverage improvement increases welfare due to offset effects.