The challenge of attribution: responsibility for population health in the context of accountable care.

One of the 3 goals for accountable care organizations is to improve population health. This will require that accountable care organizations bridge the schism between clinical care and public health. But do health care delivery organizations and public health agencies share a concept of "population"? We think not: whereas delivery systems define populations in terms of persons receiving care, public health agencies typically measure health on the basis of geography. This creates an attribution problem, particularly in large urban centers, where multiple health care providers often serve any given neighborhood. We suggest potential innovations that could allow urban accountable care organizations to accept accountability, and rewards, for measurably improving population health.