Medicare Accountable Care Organizations (ACOs) continue to improve care quality and to lower costs, according to a new report from the Centers for Medicare & Medicaid Services (CMS).

Medicare ACOs comprise hospitals, physicians groups, and other clinicians working in collaboration to coordinate care for all patients. Since the Affordable Care Act was passed, 420 Medicare ACOs have been established, caring for around 7.8 million people in the U.S., according to CMS.

“Many of these ACOs are demonstrating that they can deliver a higher level of coordinated care that leads to healthier people and smarter spending,” said CMS Acting Administrator Andy Slavitt, MBA, in a press release that accompanied the detailed report on ACO performance in 2014.

Pioneer ACOs, “the early adopters of coordinated care,” met their targets for 28 of 33 quality benchmarks — a 3.6% improvement, according to the agency. Shared Saving programs, which are a risk-averse model in comparison with Pioneer, achieved 27 of 33 quality measures in 2013 and 2014, the release stated.