Health Affairs Blog – A blog post written by Carrie Colla, assistant professor of the Dartmouth Institute for Health Policy and Clinical Practice at Geisel; Elliott Fisher, director and professor of the Dartmouth Institute for Health Policy and Clinical Practice at Geisel; Scott Heiser, policy analyst; and Emily Tierny, health policy fellow. In the post, they examine the Centers for Medicare and Medicaid Services’ recent changes to the Medicare Shared Savings Program, and accountable care organization’s (ACO) concerns about how the financial targets, which determine whether an ACO is successful at saving or guilty of overspending, are determined under the new requirements.