The social welfare function (SWF) framework is a powerful tool for evaluating governmental policies in light of human well-being. The framework originates in theoretical welfare economics and is widely used in contemporary economic scholarship, although not (yet) in governmental practice. This book is intended to provide an accessible, yet reasonably rigorous overview of the SWF approach. The framework has three components: an interpersonally comparable measure of well-being, which functions to translate outcomes into lists (“vectors”) of well-being numbers, one for each person in the population; a rule (the SWF) for ranking well-being vectors, such as the utilitarian SWF (which simply adds up well-being numbers), a continuous-prioritarian SWF (which gives greater weight to the worse off), or some other; and a procedure for ranking policies, understood as probability distributions across outcomes. Each component of the SWF framework is reviewed in detail; in doing so, the book engages both the economic literature on SWFs and philosophical scholarship regarding individual well-being, ethics, and distributive justice. The book also clarifies the difference between the SWF approach and cost-benefit analysis (CBA), which uses money rather than an interpersonally well-being measure as the scale for quantifying policy impacts. The book includes a detailed case study of risk regulation—illustrating how the SWF framework can be used in practice and how it contrasts with CBA. The book is written to be accessible to readers without much mathematical training, but is backed up by an extensive mathematical appendix.