In recent years, many health maintenance organizations (HMOs)have exited the market for Medicare managed care; since 1998, the number of participating plans has fallen from 346 to 174. As a result of this reduced participation by HMOs, hundreds of thousands of Medicare beneficiaries have been...

We seek to understand the relationship between employer decisions regarding which health plans firms choose to offer to their employees and the performance of those plans. We measure performance using data from the Health Plan Employer Data Information Set (HEDIS) and the Consumer Assessment of...