Number of ACOs in Medicare Shared Savings Program 2012-2023

Between 2012/2013 and 2018, the number of Accountable Care Organizations (ACOs) participating in the Medicare Shared Savings Program (MSSP) increased steadily from 220 to 561. The figures have fluctuated since then with a total of 483 ACOs participating in the MSSP by 2022. The ACOs collectively care for around 10.9 million beneficiaries in 2023, which is roughly one in six Medicare enrollees.
ACOs are groups of doctors, hospitals, and other health care providers, who voluntarily collaborate to achieve coordinated enhanced quality of care, reduced costs, and improved health outcomes of a designated patient population. ACOs were introduced as part of the Affordable Care Act to shift the U.S. health system from volume-based care (fee-for-service) to value-based care (alternative payment models). Most ACOs receive payment through Medicare or Medicaid, but an increasing number also contract with commercial (or private) payers.