Thanks, I agree that when to spend remains an important and non-obvious question! I'm glad to see people engaging with it again, and I think a separate post is the place for that. I'll check it out in the next few days.

I think it depends on the time horizon. If catch-up growth is not near-guaranteed in 100 years, I think waiting 100 years is probably better than spending now. If it is near-guaranteed, I think that the case for waiting 100 years ambiguous, but there is some longer period of time which would be better.

I don't think Option A is available in practice: I think the recipients will tend save too little of the money. That's the primary argument by which I have argued for Option B over giving now (see e.g. here).

But with all respect, it seems to me that you got a bit confused a few comments back about how to frame the question of when it's best to spend on an effort to spur catch-up growth, and when that was made clear, instead of acknowledging it, you've kept trying to turn the subject to the question of when to give more generally. Maybe that's not how you see it, but given that that's how it seems to me, I hope it's understandable if I say I find it frustrating and would rather not continue to engage.

No: I think that people should delay spending on global poverty/health on the current margin, not that optimal total global poverty/health spending today would be 0.

But that's a big question, and I thought we were just trying to make progress on it by focusing one one narrow angle here: namely whether or not it is in some sense "at least 1,000x better to stimulate faster economic growth in the poorest countries today than it is to do it 100 years from now". I think that, conditional on a country not having caught up in 100 years, there's a decent chance it will still not have caught up in 200 years; and that in this case, when one thinks it through, initiating catch-up in 100 years is at least half as good as doing so today, more or less.

The returns certainly aren't all that matter.

I don't follow your questions. We're comparing spending now to induce some chance of growth starting now with spending later to induce some chance of growth starting later, right? To make the scenario precise, say

• The country is currently stagnant, and its people collectively enjoy "1 util per year". Absent your intervention, it will stay stagnant for 200y.
• Spending $1m now has a 1% chance of kicking off catch-up growth.
• Investing it for 100y before spending has a 4% chance of kicking off catch-up growth then (because $868m>>$1m). The money won't be lost in the meantime (or, we can say that the chance it gets lost is incorporated into the 4%).
• In either case, the catch-up will be immediate and bring them to a state where they permanently collectively enjoy "2 utils per year".

In this case, the expected utility produced by spending now is 1%x(2-1)x200 = 2 utils.
The expected utility produced by spending in 100y is 4%x(2-1)x100 = 4 utils.

The gap can be arbitrarily large if we imagine that the default is stagnation for a longer period of time than 200y (or arbitrarily negative if we imagine that it was close to 100y), and this is true regardless of how much money the beneficiaries wind up with (due to the growth) is producing the gap between the 2 utils and the 1 util.

That depends on how long it would have stayed poor without the intervention!

I think the case for waiting is stronger, not weaker, if you think the chance that poor countries won't have exhibited catch-up growth by 2126 is non-negligible. If they haven't exhibited catch-up growth by 2126, I expect $868 million then is much more likely to trigger it than $1 million today.

I don't think trying to invest for a long time is obviously a silly strategy. But I agree that people or groups of people should decide for themselves whether they want to try to do that with their money, and a charity fundraising this year would be betraying their donors' trust if their plan was actually to invest it for a long time.

Thanks for sharing! I wasn't aware of the case for thinking that the right hemisphere has so much less welfare capacity than the left. If this is true, it leaves me thinking that the sum of the welfare capacities of the two parts of the split brain patient is significantly less than 1, rather than the 0.99 I went with in the example.

It's interesting that this EA Forum post forms so much of the basis for its answer to the second question. I wonder if it's because so little has been written on this, or just because the way you asked the question used language especially similar to this post.

Even though the Gemini report seems to represent my view (what it calls the "divisive model") and Fischer's view (the "additive model") well at first, it gets pretty confused in a few places:

1. In Section 3.1, it defines hedonistic welfare per unit time in precisely the way I'm arguing against, where there's no "size" dimension and all it means to be "a being with a higher [welfare] capacity" is that you "can experience 'deeper' pain or 'higher' pleasure".
2. It says that the divisive model is captured by the quote

"The view that expanding a mind from one hemisphere to two... would increase its welfare capacity by much less than 100%—indeed, only by something like 1%."

It then says it

reject[s] the "Strict Divisive" model because pain does not dilute with volume,

(and also rejects the "Strict Additive" model), and goes with what it frames as something in the middle, but which is fully the additive model after adjusting for the fact that, in its view, the right hemisphere lacks various capacities. -- But, despite the counterintuitive terminology it's chosen, it's the Additive view, not the Divisive view, on which "pain dilutes with volume". The Additive view says that total pain falls if you reconnect the two hemispheres of a split-brain patient in the ice bath, because a welfare subject's pain is something like an average of pain across the phenomenal field rather than a sum.

I agree that the question of when to give is very important, and that it's often underappreciated how strong of a reason compound interest is for giving later. This seems like a subject people in EA rediscover every few years and then largely forget about--it's a shame that the intricacies of the arguments back and forth get lost in the process, but good to see that people stay interested in thinking this through.

If it's helpful at all, here's a relatively comprehensive writeup of my own thoughts on the subject from three years ago (and an even older talk and podcast, for the more audio-visually inclined; and a fund some people at Founders Pledge set up for those interested in committing to long-term saving). You can also find various objections to (and elaborations on) this material from others on the EA Forum at that time, many of them excellent. I do agree with the common response that the prospect of near-term transformative AI strengthens the case for giving sooner, though not quite as straightforwardly or extremely as it might seem at first, and in fact I'm currently in the middle of writing up some thoughts on this front. But in the meantime, let me just pitch checking out the old commentary. : )