Sorting through heterogeneity of impact to enhance policy learning”

The World Bank; November 29, 2012

The demand and expec­ta­tion for con­crete pol­icy learn­ing from impact eval­u­a­tion are high. Quite often we don’t want to know only the basic ques­tion that impact eval­u­a­tion addresses: “what is the impact of inter­ven­tion X on out­come Y in set­ting Z”. We also want to know the why and the how behind these observed impacts. The World Bank impact eval­u­a­tion group fea­tures work by Angrist, Pathak, and Walters on het­ero­ge­neous treat­ment effects in their study of char­ter school effectiveness.