One in five patients in Massachusetts is now under some kind of global payment. Blue Cross Blue Shield launched this experiment in Massachusetts in 2009. Michael Chernew, and a team of researchers at Harvard Medical School, recently took a look at what happened in the first two years. The 11 physician groups and hospitals that joined in 2009 and 2010 did a better job than physicians in traditional medical contracts of making sure that patients received standard check-ups, cancer screening tests and other preventive care. Overall they trimmed spending by just under 3 percent.