Why do indemnity insurance plans cost substantially more per capita—77% more in our study—than HMOs? We answer this question using data from a large organization’s insurance pool, covering 215,000 lives. We decompose cost differences for eight major medical conditions into...

We examine why managed care plans are less expensive than traditional indemnity insurance plans. Our database consists of the insurance experiences of over 200,000 state and local employees in Massachusetts and their families, who are insured in a single pool. Within this group, average HMO...

This article describes the anatomy of health insurance. It begins by considering the optimal design of health insurance policies. Such policies must make tradeoffs appropriately between risk sharing on the one hand and agency problems such as moral hazard (the incentive of people to seek more...

This study assesses the factors influencing the movement of people across health plans. We distinguish three types of cost-related transitions: adverse selection, the movement of the less healthy to more generous plans; adverse retention, the tendency for people to stay where they are when they...