Extensive field evidence shows individuals’ decisions in settings involving choiceunder uncertainty (e.g. savings and investment choices) depend on the decisions of their peers.One hypothesized cause of peer group effects is social interaction effects: an individual’s utilityfrom an action...

This brief considers the interaction between physician incentive systems and product market competition in the delivery of medical services via managed care organizations. At the center of the analysis is the process by which health maintenance organizations (HMOs) assemble physician networks...