By identifying and analyzing all 55 studies that provide reliable causal estimates, the report provides the most complete, credible evidence to date on the post-early childhood effects of early childhood interventions. It serves three important functions. First, it provides analysis on early childhood interventions whose sustained effects have been evaluated across six areas of human development. Second, it examines how effects change—both within a population (yielding shared prosperity implications) and over time. Finally, the review aims to improve the quality and coverage of ECD knowledge by enumerating commonly observed evaluation challenges and identifying research gaps on the question of benefits beyond early childhood.