GiveWell did their first "lookbacks" (reviews of past grants) to see if they've met initial expectations and what they could learn from them:
(While I'm very glad they did so with their usual high quality and rigor, I'm also confused why they hadn't started doing this earlier, given that "okay, but did we really help as much as we think we would've? Let's check?" feels like such a basic M&E / ops-y question. I'm obviously missing something trivial here, but also I find it hard to buy "limited org capacity"-type explanations for GW in particular given total funding moved, how long they've worked, their leading role in the grantmaking ecosystem etc)
Their lookbacks led to substantial changes vs original estimates, in New Incentives' case driven by large drops in cost per child enrolled ("we think this is due to economies of scale, efficiency efforts by New Incentives, and the devaluation of the Nigerian naira, but we haven’t prioritized a deep assessment of drivers of cost changes") and in HKI's case driven by vitamin A deficiency rates in Nigeria being lower and counterfactual coverage rates higher than originally estimated: