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The Medicare Shared Savings Program (MSSP) is the largest federal initiative that promotes accountable
care and value-based payment models. A central design feature of the program is its tiered approach to
financial risk. ACOs generally begin in one-sided models and share in a portion of the savings generated but
are insulated from losses if costs exceed benchmarks. Over time, ACOs transition to two-sided
arrangements that include both shared savings and shared losses. This glidepath design reflects an
important policy insight: organizations need time to develop the infrastructure, data capabilities, and care
management processes required to successfully manage populations under risk. At the same time, the
program allows more advanced organizations to enter directly into enhanced two-sided models, aligning
their level of risk with their maturity.