Health care spending in the United States greatly exceeds that in other wealthy countries, but the U.S. does not achieve better health outcomes. Policymakers commonly attribute this spending disparity to overuse of medical services and underinvestment in social services in the U.S. However, there has been relatively little data analysis performed to confirm that assumption. Writing in JAMA, researchers led by former Commonwealth Fund Harkness Fellow Irene Papanicolas and mentor Ashish Jha, M.D., report findings from their study comparing the U.S. with 10 other high-income countries to better understand why health care spending in the U.S. is so much greater.