Mathematica informs health policy debates and addresses decision makers’ information needs through reliable data and analysis. Driven by broad-based public interest in finding ways to improve the quality, efficiency, affordability, equity, and financing of health care, we have contributed to the base of research and data in care delivery and financing, quality measures and health systems change. We also study longstanding issues, such as covering the uninsured, measuring and improving health care quality, controlling health care costs, and designing efficient and effective delivery systems to meet diverse needs.