Thanks, William, that's great to hear!
Thanks for your patience and flexibility! Though you said you weren't necessarily expecting a response, we do try to answer comments promptly, and I apologize that it took a while to get back to you on this.
This answer may not cover every question you raised, but I think it will get at most of it.
I hope that helps!
This is a big question, and one we'd very much like to have a better explanation for! It's important to note that our estimates are uncertain, so the gap between the mortality benefit of water quality interventions and mortality attributed to diarrhea is not necessarily as large as it appears. But we do find it plausible that a larger-than-expected mortality reduction would exist, for a few reasons:
For more details and citations for the above, see this section of our water quality intervention report (particularly beginning with "We are uncertain about our central estimate of the mortality impact of chlorination…").
In the course of our investigation, we also spoke to several researchers who found it plausible that water quality improvements would have a larger-than-expected mortality benefit. These researchers offered their own insight into why water treatment might also reduce non–diarrheal illness, or why the reduction in diarrhea mortality might be larger than what one would calculate indirectly from diarrhea morbidity. See our notes from these conversations here, here, and here.
In sum, we still have uncertainty about what explains the gap between mortality reduction estimates, but the impact of averting waterborne diseases on death from non-waterborne diseases probably plays a role. We think that further empirical evidence of the size of the mortality effect, or a better understanding of the mechanisms that link water quality to mortality, could help to substantially reduce our uncertainty.
Thanks for the flag, Joel.
Brian, our team is working on our own reports on how we view interpersonal group therapy interventions and subjective well-being measures more generally. We expect to publish our reports within the next 3-6 months.
We have spoken to HLI about their work, and HLI has given us feedback on our reports. It’s been really helpful to discuss this topic with Michael, Joel, and the team at HLI. Their work has provided some updates to how we view this topic, even if we do not ultimately end up reaching the same conclusions.
We’re still looking into this area and some of the important questions HLI has raised. While we plan to provide a more detailed view once our reports are published, a few areas where we differ from HLI are below:
We still have a lot of uncertainty about how to compare different interventions like cash transfers and therapy, and making these comparisons is crucial to our decisions on what funding opportunities to recommend to our donors. As a result, we hope to continue to discuss this topic with individuals who have a differing view than us on our moral weights so that we can continue to refine our approach.
We look forward to engaging once we publish a fully vettable report. Until then, I hope this answers the immediate questions you have about where the views of GiveWell and HLI differ.