A study of the quality of care given by doctors while the pay-for-performance incentives were rolling out in Massachusetts shows they didn't make a difference. Researchers from Massachusetts General Hospital, Harvard, Harvard Pilgrim Health Care, and Massachusetts Health Quality Partners report that clinical quality got better in Massachusetts between 2001 and 2003 across the board. They studied doctors groups whose income was tied to a series of measures, such as how many patients got mammograms or had their diabetes monitored.