While only 21% of Track 1 ACOs that joined the MSSP in 2017 earned savings, almost half of those who have participated for at least five performance years (46%) were able to lower costs enough to earn shared savings The Proposed Pathways to Success rule expects all renewing or re-entering ACOs to be ready and willing to take on risk by their second full performance year, and new entrants to be ready by their third (i.e.