“Is Extinction Risk Mitigation Uniquely Cost-Effective? Not in Standard Population Models” by Vasco Grilo🔸

This is a linkpost for Is Extinction Risk Mitigation Uniquely Cost-Effective? Not in Standard Population Models by Gustav Alexandrie and Maya Eden, which was published on 18 August 2025 as chapter 20 of the book Essays on Longtermism: Present Action for the Distant Future. I got Claude Opus 5 to write the summary and 2 objections below after some iteration. The objections came from me. Gustav said the summary "looks correct from very quickly skimming it, though I may well have missed if there are mistakes". I also think it is accurate based on my read of the article. Thanks to Gustav for feedback on the draft objections, and pushing me to shorten the summary, which now has 1/3 as many words as the main text of the chapter (excluding abstract, footnotes, references, and appendix).

TL;DR

Alexandrie and Eden take aim at the long-run argument for prioritising extinction risk mitigation: the Parfit-derived claim that the gap between a 99% catastrophe and a 100% catastrophe dwarfs the gap between no catastrophe and a 99% one, because extinction alone forecloses all future generations. They grant the argument's ethics entirely — total, time-neutral aggregation of welfare — and attack the demography it [...]

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Outline:

(01:04) TL;DR

(02:44) 1. The target argument

(04:48) 2. The framework: the long-term value ratio

(07:36) 3. Pure population shocks: three models

(10:49) 4. Shocks to all factors of production: the robust result

(12:18) 5. The back-of-the-envelope calculation

(15:19) 6. Increasing the stock of natural resources

(16:42) 7. Conclusions

(17:51) 8. Two things I'd push on

(17:55) 8.1. The model's separability across events is doing real work

(21:28) 8.2. A minor note on the space-expansion contrast

(24:12) References

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First published:
August 24th, 2026

Source:
https://forum.effectivealtruism.org/posts/qPHu48NrqnoD8xyat/is-extinction-risk-mitigation-uniquely-cost-effective-not-in

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Narrated by TYPE III AUDIO.