Pioneer program
After the Pioneer program launched, the Medicare Shared Savings Program (MSSP) was established by section 3022 of the Affordable Care Act. It is the program by which a US ACOs interact with the federal government, and by which ACOs can be created. It is a fee-for-service model. The MSSP had a much larger scope than the Pioneer program. It offered four tracks for ACOs: 1, 1+, 2, and 3. Track 1 was the most popular, with more than 80% of ACOs selecting it; this allowed the ACOs to avoid the possibility of shared loss.