Colorado is partnering with Medicare to pay doctors based on whether they can keep patients healthy.

Colorado is one of four states partnering with Medicare to try to pay doctors based on whether they can keep their patients healthy, but it’s not clear how they’re going to do that.

The idea that insurers can keep costs down by encouraging the kind of care that keeps people from needing costlier procedures down the road isn’t new, and Medicare has tried a mix of incentives and financial punishments over the last decade.

Most haven’t generated significant savings or shown they improve patients’ health, and the American health care system still primarily relies on billing for individual services.

Part of the reason that efforts to pay for quality haven’t achieved much is that Medicare, Medicaid and private insurers are each going their own way, with separate measures of care quality and different ways of paying, said Karen Joynt Maddox, co-director of the Center for Health Economics and Policy at Washington University.