The OIG has examined the results of the first three years of the Medicare Shared Savings Program, under which accountable care organizations (ACOs) coordinate care to reduce Medicare costs and improve quality of care. The OIG reports that 428 participating ACOs serving 9.7 million beneficiaries saved almost $1 billion in net Medicare spending while generally improving quality of care.  The results among individual ACOs varied significantly, however.  The OIG determined that 58 “high-performing ACOs” reduced spending by an average of $673 per beneficiary for key Medicare services during the review period, while 122 other Shared Savings Program ACOs (and fee-for-service providers) increased per beneficiary spending for these services.  The OIG observed that understanding the success of high-performing ACOs “can inform not only the future direction of the Shared Savings Program, but also alternative payment models that seek to achieve high-quality care for lower costs.”