Within the Medicare program, we expected the MA group to exhibit the lowest spending over the years we observed because Banner faced financial risk throughout the period, whereas the ACO did not begin until 2012. We also expected the ACO group to exhibit slower growth in use and cost than the TM comparison group after the ACO was established. In fact, the MA group did have the lowest spending of the 3 groups, driven by the lowest use of hospital and postacute services.
Newhouse, Joseph P., Mary Price, John Hsu, Bruce Landon, and J. Michael McWilliams. "Currently Reading Delivery System Performance as Financial Risk Varies." The American Journal of Managed Care (December 2019).