Physician groups are primary ACO sponsors

As of January, there are 428 total accountable care organizations, including commercial and Medicare ACOs, in 49 states, Health Affairs reported. More than 250 ACOs partipate in the Medicare Shared Savings Program and cover up to 4 million Medicare beneficiaries. "Physician groups have overtaken hospital systems and have now become the largest backer of ACOs," wrote David Muhlestein in a blog post at Health Affairs. Blog Post