[영문]The lack of good information on providers’ performance is an impediment to improving the affordability and quality of health care. Knowing that certain hospitals or physicians produce more effective and efficient care would help consumers make appropriate purchases and create incentive for improvement. Yet many physicians resist such measurement efforts, unconvinced of their accuracy. Meanwhile, large employers want much more than their insurers provide to them, including attribution of quality and cost of care to individual physicians. Although recent developments in performance measurement illustrate its unsettled state, they also foreshadow how the field may advance.