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 in changes either in the number of people affected or only in the identities of these people.
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.