An account of collective actions in public health.

Aggregated health decisions by individuals are of paramount importance to public health professionals and policymakers, especially in situations where collective participation is a prerequisite for achieving an important public health goal such as herd immunity. In such circumstances, concerted action often falls short of the common good through lack of sufficient participation. Collective action problems are traditionally attributed to rational egoists seeking to promote their interests and enjoy a "free ride." We call attention, however, to the behavioral features of collective action and their implications for solving public health policy problems.