Listen now (32 mins) | Listen Now The Medicare Shared Savings Program's Accountable Care Organization (ACOs), created by Section 3022 of the 2010 Affordable Care Act constitutes the flagship Medicare pay for performance (P4P) program. Though there are other P4P (also termed pay for value) models, for example two bundled payment models (Bundled Payments for Care Improvement and Comprehensive Care for Joint Replacement), they are short-lived CMS demonstrations. If the federal government is to bend the Medicare spending curve or make the program more financially sustainable it will likely be due moreover to the success of ACOs. Though provider participation in ACOs is substantial, this year there are 561 ACOs providing care to 10.5 million Medicare beneficiaries, the program has to date achieved marginal success. Over four performance years (2013-2016), ACOs have saved substantially less than one percent of annual Medicare spending (now over $700 billion) - which is why the DHHS Secretary Alex Azar recently admitted candidly ACO performance has been "underwhelming" and "lackluster." Even before the Medicare ACO program formally began there have been questions and criticism about the model's design. Perhaps no one has written more about the model's flaws than Kip Sullivan.