By some measures, well over half of charities do little or no good. When similar charities are compared, the most effective ones can be up to 100 times more effective than the least. And there’s often a big mismatch between where donors direct their support and where the need and potential benefits are greatest.

A movement called effective altruism aims to make giving work better by identifying the most effective charities in the world and encouraging donors to support them generously and strategically.

There's been a lot of excitement about it, but lately it's also drawn critics of its ethical premises and the behavior of some who call themselves effective altruists.

In this episode Spencer explores both the promise challenges of effective altruism, in a fascinating conversation with one of the movement’s leaders, Luke Freeman, Executive Director of Giving What We Can.