I believe there’s an important case where this does actually matter.
Suppose there’s a fundraising charity F which raises money for charities X and G. Charity X is an x-risk charity, and F raises money for it at a 2:1 ratio. Charity G is a global poverty charity, and F raises money for it at a 10:1 ratio. If you care more about x-risk than global poverty and believe charity G decreases x-risk, or only increases x-risk by a tiny amount, then you should give to F instead of X. But if G increases x-risk by more than 20% as much as X decreases it, then giving to F is actually net negative and you should give to X instead.
I don’t believe 20% is implausibly high. This only requires that ending global poverty increases x-risk by about 0.01% and charity G is reasonably effective. (I did some Fermi calculations to justify this but they’re pretty complicated so I’ll leave them out.)
I believe there’s an important case where this does actually matter.
Suppose there’s a fundraising charity F which raises money for charities X and G. Charity X is an x-risk charity, and F raises money for it at a 2:1 ratio. Charity G is a global poverty charity, and F raises money for it at a 10:1 ratio. If you care more about x-risk than global poverty and believe charity G decreases x-risk, or only increases x-risk by a tiny amount, then you should give to F instead of X. But if G increases x-risk by more than 20% as much as X decreases it, then giving to F is actually net negative and you should give to X instead.
I don’t believe 20% is implausibly high. This only requires that ending global poverty increases x-risk by about 0.01% and charity G is reasonably effective. (I did some Fermi calculations to justify this but they’re pretty complicated so I’ll leave them out.)