I struggle to follow the logic that would permit this risk taking in the first place, even without all these caveats. As you said:
a foundation with $15 billion would end up being a majority of funding for those areas, and so effectively increase the resources going towards them by more than 2-fold, and perhaps as much as 5-fold… by contrast… $15 million from me, spread out over a period of years, would represent less than a 1% increase.
This is indeed a big difference. If you’re looking at a small-ish donation, it makes sense to ask if it’s uncorrelated with other similar donations, and of yes to take the option with the higher expected value, because over a large number of such choices it’s probable that the average donation would indeed have that value. In contrast, if you’re looking at a donation in the billions of dollars, this EV logic is almost entirely irrelevant—even if it were uncorrelated with other donations, you don’t have a hundred or a thousand donations of this size! The idea that we can actually expect do get the EV is just wrong. We in fact never get it.
So you can decide to be more or less risk averse, but you can’t really pretend you’re not risking a billion dollars here and hide behind EV maximisation.
I struggle to follow the logic that would permit this risk taking in the first place, even without all these caveats. As you said:
This is indeed a big difference. If you’re looking at a small-ish donation, it makes sense to ask if it’s uncorrelated with other similar donations, and of yes to take the option with the higher expected value, because over a large number of such choices it’s probable that the average donation would indeed have that value. In contrast, if you’re looking at a donation in the billions of dollars, this EV logic is almost entirely irrelevant—even if it were uncorrelated with other donations, you don’t have a hundred or a thousand donations of this size! The idea that we can actually expect do get the EV is just wrong. We in fact never get it.
So you can decide to be more or less risk averse, but you can’t really pretend you’re not risking a billion dollars here and hide behind EV maximisation.