Effective altruism is the use of evidence and careful reasoning to work out how to maximize positive impact on others with a given unit of resources, and the taking of action on that basis. It’s a philosophy and a social movement that is gaining considerable steam in the philanthropic world. For example, GiveWell, an organization that recommends charities working in global health and development and generally follows effective altruist principles, moves over $90 million per year to its top recommendations. Giving (...) What We Can, which encourages individuals to pledge at least 10% of their income to the most cost-effective charities, now has over 3500 members, together pledging over $1.5 billion of lifetime donations. Good Ventures is a foundation, founded by Dustin Moskovitz and Cari Tuna, that is committed to effective altruist principles; it has potential assets of $11 billion, and is distributing over $200 million each year in grants, advised by the Open Philanthropy Project. [...] GPI Working Paper No. 8-2019. (shrink)