Our guest Holden Karnofsky joins us to discuss Givewell, the nonprofit organization he founded. Givewell is devoted to investigating charities and NGOs to determine how much of an impact they're having. You could call it "evidence-based philanthropy." He discusses how Givewell evaluates charities, and what the research has to say about various controversies as well as the conventional wisdom in the nonprofit world: Can large charities be efficient? Is the percentage of the donation that goes to expenses really a useful metric? Should we focus on problems closer to home instead of giving to foreign countries? Do microfinance NGOs like Kiva or Grameen Bank live up to their claims? And should or can charities be evaluated objectively?