The Trump administration is proposing to restrict an innovation in the Affordable Care Act (ACA) that was intended to improve Medicare and slow spending in the vast federal insurance system for older Americans. Health care researchers have hailed the model's promise to improve quality and efficiency, but government data suggest it is not saving enough money. The changes, announced Thursday by the administrator of the Department of Health and Human Services' Centers for Medicare and Medicaid Services, would significantly curtail accountable care organizations (ACOs). The ACOs can be teams of doctors, hospitals, or other providers who become responsible for all the health care needs of a specific group of patients. (Amy Goldstein, Washington Post)