Substantial Physician Turnover And Beneficiary 'Churn' In A Large Medicare Pioneer ACO.

Alternative payment models, such as accountable care organizations (ACOs), attempt to stimulate improvements in care delivery by better alignment of payer and provider incentives. However, limited attention has been paid to the physicians who actually deliver the care. In a large Medicare Pioneer ACO, we found that the number of beneficiaries per physician was low (median of seventy beneficiaries per physician, or less than 5 percent of a typical panel). We also found substantial physician turnover: More than half of physicians either joined (41 percent) or left (18 percent) the ACO during the 2012-14 contract period studied. When physicians left the ACO, most of their attributed beneficiaries also left the ACO. Conversely, about half of the growth in the beneficiary population was because of new physicians affiliating with the ACO; the remainder joined after switching physicians. These findings may help explain the muted financial impact ACOs have had overall, and they raise the possibility of future gaming on the part of ACOs to artificially control spending. Policy refinements include coordinated and standardized risk-sharing parameters across payers to prevent any dilution of the payment incentives or confusion from a cacophony of incentives across payers.