Hey Nick, thanks for raising this question about the plausibility of chlorination’s effect of mortality and the need for more research to understand why. I’m a senior researcher at GiveWell and wanted to chime in with a little more context.
When we did our analysis, we agreed that the ~25%-30% headline figure from the Kremer et al. meta-analysis felt implausibly high. We end up with estimates of ~5%-15% depending on the country and program (e.g., ~6% for the Dispensers for Safe Water Program in Uganda and ~12% for the in-line chlorination program in Malawi).
A bit more on what we did:
These mortality effect estimates are really uncertain, though, so we’ve funded follow-up research (as Dan alluded to in his comment).
Thanks again for boosting this question — it’s something we’ve been thinking about a lot, and I’m glad it’s getting some more attention. I think we’d be open to hearing more thoughts about how we could learn more about the extent to which chlorination affects mortality and why, since we’re continuing to explore more grants to chlorination.
We just don't want to give an unfair advantage to applicants who have previously seen a version of the trial task that might be in use by the time they apply.