This work draws heavily on the Moral Weight Project from Rethink Priorities and relies on the same assumptions: utilitarianism, hedonism, valence symmetry, unitarianism, use of proxies for hedonic potential, and more. Although I think the Rethink Priorities welfare range estimates are currently the best tool available for interspecies welfare comparisons, I do not necessarily endorse these assumptions in full, nor do I think the Rethink Priorities welfare ranges are the “correct” weights—only the best available.
These are some pretty big assumptions. In particular, when they discussed the sensitivity to the hedonism assumption, ReThink argued that this simplifying assumption wasn’t a big deal, because relaxing it would only make a 3x difference or so, and this was not relevant for cause prioritization:
We suggest that, compared to hedonism, an objective list theory might 3x our estimate of the differences between humans’ and nonhumans’ welfare ranges. But just to be cautious, let’s suppose it’s 10x. While not insignificant, that multiplier makes it far from clear that the choice of a theory of welfare is going to be practically relevant. To see this, recall that Open Philanthropy once estimated that “[if] you value chicken life-years equally to human life-years, this implies that corporate campaigns do about 10,000x as much good per dollar as top [global health] charities.”
But your human vs all-nonhuman lines are sufficiently close that a 3x, let alone a 10x, difference would reverse the bottom line conclusion. I think it does make a considerable difference that the argument they use for ‘why we don’t need to worry about this assumption’ doesn’t apply here, given that pure hedonism is basically the least-favourable theory of welfare to use here.
These are some pretty big assumptions. In particular, when they discussed the sensitivity to the hedonism assumption, ReThink argued that this simplifying assumption wasn’t a big deal, because relaxing it would only make a 3x difference or so, and this was not relevant for cause prioritization:
But your human vs all-nonhuman lines are sufficiently close that a 3x, let alone a 10x, difference would reverse the bottom line conclusion. I think it does make a considerable difference that the argument they use for ‘why we don’t need to worry about this assumption’ doesn’t apply here, given that pure hedonism is basically the least-favourable theory of welfare to use here.
(As it happens I also think that their attempt to bound the importance of non-hedonic factors at 3x or 10x doesn’t work, because their thought experiments about Tim only consider relatively weak non-hedonic goods).