Book excerpt: A revolutionary approach to poverty that takes human irrationality into account-and unlocks the mystery of making philanthropic spending really work. American individuals and institutions spent billions of dollars to ease global poverty and accomplished almost nothing. At last we have a realistic way forward. Presenting innovative and successful development interventions around the globe, Dean Karlan and Jacob Appel show how empirical analysis coupled with the latest thinking in behavioral economics can make a profound difference. From Kenya, where teenagers reduced their risk of contracting AIDS by having more unprotected sex with partners their own age, to Mexico, where giving kids a one-dollar deworming pill boosted school attendance better than paying their families to send them, More Than Good Intentions reveals how to invest those billions far more effectively and begin transforming the well-being of the world.