Consulting firm Oliver Wyman estimates there are now 522 accountable care organizations serving 15-17% of the U.S. population.

These figures are from the firm’s latest report, available here. It contains several key statistics on the model’s growth.

The 522 total ACOs is an increase from 370 in September 2013 and 258 in February 2013. The majority of these are Medicare-directed ACOs — Pioneer ACOs, Medicare Shared Savings Program ACOs, Medicaid ACOs, or participants in the Physician Group Practice Transition program. CMS’ latest round of ACO approvals in January brings the total number of Medicare ACOs to 368, up from 235 in July 2013. Despite their target populations, the Medicare ACOs are still serving an estimated 33 million non-Medicare patients, according to the report.

There are about 155 non-Medicare ACOs in operation across the country, a 14% increase from 135 in July 2013 and a 24% rise from 124 in January 2013.