REVISED PROJECT SUMMARY/ABSTRACT Project 5 will leverage the quality judgments of market participants (physicians and patients) to study the underlying market for quality within Medicare. A key objective of the Medicare program is to ensure that beneficiaries receive high-quality care. Yet there is wide variation in quality and evidence of diminished health outcomes for many patients due to deficient care. Medicare has pursued pay-for-performance and public reporting initiatives to improve quality, but these strategies have had limited impact, raising the need for new policy approaches. In theory, market forces should incentivize quality improvement by rewarding high-quality providers with more patients and high-quality organizations with physician labor. In practice, demand for provider quality may be weakened by market failures, including limited information and barriers to switching. This project will deepen understanding of the market for quality by assessing the quality perceptions of market participants and the barriers to acting on this information. Although we will also draw from standard quality metrics, the project’s primary focus is a novel compilation of quality judgments made by physicians and patients. We will capture the medical profession’s perceptions of physician quality using residency evaluations, board exam scores, and physicians’ choice of providers for their own care (as physicians are among the best-informed consumers of health care). We will capture physicians’ judgments of organization quality using employee surveys and their revealed preferences as patients. And we will assess patient perspectives using survey data and revealed preferences. Given the challenges of quality measurement, the judgments of the most informed actors in the system are likely to reveal important and understudied information. Furthermore, these perceptions may drive care, referral, and employment decisions more strongly than standard measures used for public report