Early childhood policymakers need to understand not only where public funds are invested, but whether those investments are achieving their intended goals. This brief, part of a series on Early Childhood Integrated Data Systems (ECIDS) co-authored by the Center for Early Learning Funding Equity (CELFE) and the Chicago Early Childhood Integrated Data System (CECIDS), explores how states can build evaluation capacity to turn integrated data into evidence for better public investments. It examines the analytic expertise, consistent methods, and responsible data governance needed to evaluate policy effectiveness and inform future budget decisions.