Building regulatory and operational flexibility into accountable care organizations and 'shared savings'.

The Affordable Care Act created accountable care organizations (ACOs), which will be a new part of Medicare as of January 2012, together with a "shared savings program" that will modify how these organizations will be paid to care for patients. Accountable care organizations have the potential to lower costs, improve the quality of care, facilitate delivery system reform, and promote innovation in health care. The federal government is set to create rules to regulate these organizations and has broad discretion to allow them to pursue a variety of approaches. Drawing on experience from some ACO pilot programs and the Medicare Part D prescription drug coverage program, we argue that regulations governing accountable care organizations should be flexible, encouraging of diversity and innovation and allowing for changes over time based on lessons learned. We recommend using regulations as a general framework, while relying on notices and other guidance below the regulatory level to spell out specific requirements.