Data are from the Centers for Medicare and Medicaid Services (CMS) public release
file and the National Survey of ACOs (NSACO) (N=137; cohort consistent over all
3 years). The NSACO response rate was 71% among eligible ACOs. Physician-group
ACOs are ACOs consisting only of physician groups and no other provider types. Hospital-coalition ACOs are ACOs that are not integrated delivery systems and that include a hospital. Mean number of clinicians is the number of full-time-equivalent
primary care and specialty clinicians participating in the ACO. Proportion of ACOs achieving savings comes from publicly available CMS data.