Imagine you have a few million dollars. You want to spend it on the poor. How do you go about it? Billions of government dollars, and thousands of charitable organizations and NGOs, are dedicated to helping the world’s poor. But much of their work is based on assumptions about the poor and the world that are untested generalizations at best, harmful misperceptions at worst.

Abhijit V. Banerjee and Esther Duflo have pioneered the use of randomized control trials in development economics through their award-winning Poverty Action Lab. They argue that by using randomized control trials, and more generally, by paying careful attention to the evidence, it is possible to make accurate-and often startling assessments-on what really impacts the poor and what doesn’t