Robert Berenson and Teresa Coughlin conducted case studies of five health plans that received high scores on quality and resource utilization, using data collected by the National Committee for Quality Assurance. The study's focus was how health plans with delivery systems with a significant network of independent physicians achieve high performance. Plan leaders identified the following factors: building a physician-plan partnership, establishing the plan as a resource for practices, providing physician data on performance, and having a local area orientation. Because employers are primarily responsible for arranging the health insurance coverage for their employees, there is market pressure for health plans to work with broader networks than they would otherwise want, which in turn interferes with the factors that lead to high performance.