Risk selection and risk adjustment in competitive health insurance markets
Layton, Timothy James
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In most markets, competition induces efficiency by ensuring that goods are priced according to their marginal cost. This is not the case in health insurance markets. This is due to the fact that the cost of a health insurance policy depends on the characteristics of the consumer purchasing it, and asymmetric information or regulation often precludes an insurer from matching the price an individual pays to her expected cost. This disconnect between cost and price causes inefficiency: When the premiums paid by consumers do not match their expected costs, consumers may sort inefficiently across plans. In this dissertation, I study the effects of policies used to alleviate selection problems. In Chapter 1, I develop a model to study the effects of risk adjustment on equilibrium prices and sorting. I simulate consumer choice and welfare with and without risk adjustment in the context of a Health Insurance Exchange. I find that when there is no risk adjustment, the market I study unravels and everyone enrolls in the less comprehensive plan. However, diagnosis-based risk adjustment causes over 80 percent of market participants to enroll in the more comprehensive plan. In Chapter 2, we study an unintended consequence of risk adjustment: upcoding. When payments are risk adjusted based on potentially manipulable risk scores, insurers have incentives to maximize those risk scores. We study upcoding in the context of Medicare, where private Medicare Advantage plans are paid via risk adjustment but Traditional Medicare is not. We find that when the same individual enrolls in a private plan her risk score is 5% higher than if she would have enrolled in Traditional Medicare. In Chapter 3, we study two forms of insurance for insurers: Reinsurance and risk corridors. Protecting insurers from risk can lower prices and improve competition by inducing entry into risky markets. It can also induce inefficiencies by causing insurers to manage risk less carefully. We use simulations to compare the power of reinsurance and risk corridors to protect insurers against risk while limiting efficiency losses. We find that risk corridors are always able to limit insurer risk with the lowest efficiency cost.