Health care in the United States is more expensive than in other developed countries, costing $2.7 trillion in 2011, or 17.9 percent of the national gross domestic product. Increasing costs strain budgets at all levels of government and threaten the solvency of Medicare, the nation's largest health insurer. At the same time, despite advances in biomedical science, medicine, and public health, health care quality remains inconsistent. In fact, underuse,...