I review the complex welfare economic issues that arise in environmental decision-making over very long periods, as in cases relating to climate change and biodiversity loss. I also consider the issues that arise in choosing a discount rate to apply to very long-run projects and indicate how...

A long-standing challenge for welfare economics is to develop welfare criteria that can be applied to allocations with different population levels. Such a criterion is essential to resolve the optimal population problem, i.e., the tradeoff between population size and the welfare of each person...