The Hidden Cost of Attribution Drift: Why ACO Performance Breaks Long Before Scores Are Released

Many ACOs quietly lose ground on performance in Q1, long before quality scores or shared savings reports arrive. Attribution drift—when the population you are accountable for no longer matches how care is staffed, managed, and delivered—silently erodes care management efficiency, quality measure performance, and financial predictability. Left unmanaged, it turns January’s “quiet” reporting period into the moment when performance problems are locked in for the rest of the year. This article explains how attribution drift starts, the early warning signs leaders should watch, and how proactive attribution governance can protect both outcomes and teams by treating attribution as a core leadership responsibility, not a static CMS output.