Poor countries need development programs that are both effective and cost-effective. To assess effectiveness, researchers are increasingly using randomized trials (or quasi-experimental methods that imitate randomized trials), which provide a clear picture of which outcomes are attributable to the program being evaluated. This "Policy Insight"…

We review what is known about Head Start's impacts on children and argue that the program is likely to generate benefits to participants and society as a whole that are larger than program costs. Our conclusions differ from those in some previous reviews because we use a more appropriate standard to judge program effectiveness (benefit-cost…