Utilitarianism, Prioritarianism, and Climate Change: A Brief Introduction

Abstract

This chapter compares prioritarianism and utilitarianism as frameworks for evaluating climate policies. Prioritarianism is an ethical view that gives greater weight to well-being changes affecting worse-off individuals. This view has been much discussed in recent moral philosophy but, thus far, has played little role in scholarship on climate change—where the utilitarian approach has, to date, been dominant. Prioritarianism and utilitarianism can be operationalized as policy-evaluation methodologies using the formalism of the “social welfare function” (SWF). Outcomes are converted into vectors (lists) of well-being numbers, one for each person in the population of concern. These lists are then ranked using some rule. The dominant approach in climate economics is to employ a discounted-utilitarian SWF. Well-being numbers are multiplied by a discount factor that decreases with time; these discounted numbers are then summed. The discounted-utilitarian SWF is problematic, both in incorporating an arbitrary preference for earlier generations, and in ignoring the well-being levels of individuals affected by policies. By contrast, the non-discounted prioritarian SWF eschews a discount factor, and adjusts well-being numbers so as to give priority to the worse off. This chapter describes the discounted-utilitarian and nondiscounted-prioritarian SWFs, and compares them with reference to three important topics in climate policy: the Ramsey formula, the social cost of carbon, and optimal mitigation.