How do economists persuade their readers that one policy is superior to another? A glance at the literature on welfare economics quickly provides the answer to this question: Economists enter policy debates armed with mathematical models, evaluating options on the basis of their consequences. Economists typically classify a policy change as a welfare improvement with respect to the status quo if the gain realized by the winners exceeds the harm sustained by the losers. The best policy becomes the one that (...) generates the highest net benefit. (shrink)