When then-hedge fund manager Elie Hassenfeld began his philanthropic journey in 2006, he knew that he wanted to get the most charitable bang for his buck. He quickly realized, however, that detailed data on charitable impact simply didn't exist. So he and Holden Karnovsky founded GiveWell, an organization inspired by effective altruism that identifies the charities that save or improve lives the most for every dollar given. Listen as Hassenfeld, GiveWell's CEO, explains to EconTalk's Russ Roberts how GiveWell determines the small number of charities they recommend to achieve optimal impact. They also discuss the dangers of an over-reliance on data and the case for bucketing our philanthropy to allow for local or personal giving.