Suicide Hotlines: One of the reasons I estimated crisis chat/suicide hotlines as having as high an impact as I did was visitors’ self-reports. Since then I saw a discussion of leafleting on FB, where several people said they had high priors for it working because when they leafleted, some people seemed really interested and said they were going to change. My reading of the quantitative research is that there’s no proof leafleting has any effect, so I should discount my own estimates of crisis chat. I also completely failed to account for the damage a bad counselor can do. I found one metastudy on the effect of suicide hotlines, and it appears debatable they’re accomplishing anything, much less have a good cost:benefit ratio.
I may also be pessimistic because I had two people initiate attempts while they were talking to me in a month.
Blood donation: I was hoping to talk to the actual blood bank, but they’re no longer returning my e-mails and this has gone on too long. I stand by the calculations for average effectiveness, but after a discussion with Alexander Berger I am retracting the claim for marginal effectiveness. New donors can apparently be recruited rather cheaply. There are concerns that the blood is more likely to carry infection (not all of which can be caught by testing), or that incentives will crowd out more altruistic donations, or that the marginal cost will grow with time, but these have the whiff of valuing moral purity over results. You could convince me otherwise, but at this point it needs data. On the other hand, blood donation may have health benefits, especially if you don’t menstruate (thanks to Kate Donovan for pointing this out).