The Medicare Shared Savings Program (MSSP) adjusts savings benchmarks by beneficiaries' baseline risk scores. To discourage increased coding intensity, the benchmark is not adjusted upward if beneficiaries' risk scores rise while in the MSSP. As a result, accountable care organizations (ACOs) have an incentive to avoid increasingly sick or expensive beneficiaries. We examined whether beneficiaries' exposure to the MSSP was associated with within-beneficiary changes in risk scores and whether risk scores were associated with entry to or exit from the MSSP. We found that the MSSP was not associated with consistent changes in within-beneficiary risk scores. Conversely, beneficiaries at the ninety-fifth percentile of risk score had a 21.6 percent chance of exiting the MSSP, compared to a 16.0 percent chance among beneficiaries at the fiftieth percentile. The decision not to upwardly adjust risk scores in the MSSP has successfully deterred coding increases but might discourage ACOs to care for high-risk beneficiaries in the MSSP .