Abstract: In recent years, governments have become keenly interested in behavioral science; new findings in psychology and behavioral economics have led to bold initiatives in areas that involve poverty, consumer protection, savings, health, the environment, and much more. Private institutions have used behavioral findings as well. But there is a pervasive and insufficiently explored question: when is it best to ask people to make active choices, and when is it best to use a default rule, which means that people need not make any choice at all? The answer depends on a form of cost–benefit analysis, which means that it is necessary to investigate whether choosing is a burden or a pleasure, whether learning is important, and whether a default rule would satisfy the informed preferences or all of most people.