Population ethics is the branch of normative ethics that attempts to justify and articulate principles for making choices between alternatives involving different people. These differences can consist of changes either in the number of people affected or only in the identities of these people.

Further reading

Aird, Michael (2020) Collection of evidence about views on longtermism, time discounting, population ethics, significance of suffering vs happiness, etc. among non-EAs, Effective Altruism Forum, May 10.
Many additional resources with some relevance to this topic.

Arrhenius, Gustaf, Jesper Ryberg & Torbjörn Tännsjö (2006) The repugnant conclusion, Stanford Encyclopedia of Philosophy, February 16 (updated 16 January 2017).

Greaves, Hilary (2017) Population axiology, Philosophy Compass, vol. 12, pp. 1–15.

Karnofsky, Holden (2022) Debating myself on whether “extra lives lived” are as good as “deaths prevented”, Cold Takes, March 29.
An engaging yet rigorous introduction to some of the key issues in population ethics in the form of an imaginary dialogue between a proponent and an opponent of total utilitarianism.

MacAskill, William & Darius Meissner (2020) Population ethics: The total view, in 'Elements and types of utilitarianism', Utilitarianism.

axiology | ethics of existential risk | Jeff McMahan | Derek Parfit