This essay is a survey of utilitarian criteria aimed at guiding what Parfit (1984) called Different Number Choices (i.e. choices affecting both people’s number and identities). The emphasis is laid on two aspects of those criteria: their ethical foundations and their implications. Our analysis...

In A Mathematical Theory of Saving (1928), Frank Ramsey not only laid the foundations of the fruitful optimal growth literature, but also launched a major moral debate: should we discount future generations’ well-being? While Ramsey regarded such “pure” discounting as “ethically...

Whereas existing OLG models with endogenous longevity neglect the impact of environmental quality on mortality, this paper studies the design of the optimal public intervention in a two-period OLG model where longevity is influenced positively by health expenditures, but negatively by pollution...

This paper re-examines the spaceship problem, i.e. the design of the optimal population under the environmental constraint of a fixed area available for life, by focusing on the dilemma between adding new beings and extending the life of existing beings. For that purpose, we characterize, under...