The unhealthy state of health policy research.

Health policies often represent large-scale natural experiments with poorly understood risks and benefits. Unfortunately, researchers often stray from the core principles of study design required to provide valid evidence. The result is that policymakers and the public do not always know what to believe. We illustrate the problem in several fields, including pay-for-performance, cost sharing, and health information technology policies. We suggest a few ways to improve health policy research so that evidence can inform policy more often. The way forward should include more credible data for those making the hard trade-offs between cost and quality of care.