This could happen for two reasons: either the 2019 recommended charities run out of room for more funding, or GiveWell finds a charity that’s better than any of the 2019 recommendations.
I think the third reason that you mention later is more likely, namely that “Perhaps instead Metaculus expects GiveWell’s estimate is currently too pessimistic, and it will converge on the true answer by 2031.”
This seems most likely to me since my guess is that the reason why GiveWell’s estimate changed from $890 in 2016 to $436 in 2019 is because their methodology or something else changed (e.g. 2019-GiveWell thought 2016-GiveWell’s way of estimating the “cost to get an outcome as good as saving a life” over-estimated the true cost). I don’t think they actually believe the best giving opportunity was twice as cost-effective in 2019 as 2016. (I don’t actually know this for sure, so if you or someone else knows better, please correct my guess.)
This at least weakly suggests that Metaculus users expect GiveWell to improve its recommendations over time.
Does it? If “the 2019 recommended charities run out of room for more funding” this could be because e.g. governments or billionaires have stepped in to make sure that every child who needs one has a bed net and all deworming efforts have been fully funded forever. It seems to me that this would mean that the marginal philanthropist no longer has access to this low-hanging fruit. Since these opportunities would be fully-funded, GiveWell would then have to recommend the next best thing, which would be less cost-effective in expectation, not more.
I think the third reason that you mention later is more likely, namely that “Perhaps instead Metaculus expects GiveWell’s estimate is currently too pessimistic, and it will converge on the true answer by 2031.”
This seems most likely to me since my guess is that the reason why GiveWell’s estimate changed from $890 in 2016 to $436 in 2019 is because their methodology or something else changed (e.g. 2019-GiveWell thought 2016-GiveWell’s way of estimating the “cost to get an outcome as good as saving a life” over-estimated the true cost). I don’t think they actually believe the best giving opportunity was twice as cost-effective in 2019 as 2016. (I don’t actually know this for sure, so if you or someone else knows better, please correct my guess.)
Does it? If “the 2019 recommended charities run out of room for more funding” this could be because e.g. governments or billionaires have stepped in to make sure that every child who needs one has a bed net and all deworming efforts have been fully funded forever. It seems to me that this would mean that the marginal philanthropist no longer has access to this low-hanging fruit. Since these opportunities would be fully-funded, GiveWell would then have to recommend the next best thing, which would be less cost-effective in expectation, not more.