Timur Kuran* and Cass R. Sunstein

An availability cascade is a self-reinforcing process of collective belief formation by which an expressedperception triggers a chain reaction that gives the perception increasing plausibility through its rising availability in public discourse. Thedrivingmechanisminvolvesacombinationofinformationaland reputational motives: Individuals endorse the perception partly by learning from the apparent beliefs of others and partly by distorting their public re- sponses in the interest of maintaining social acceptance. Availability entrepre- neurs–activists who manipulate the content of public discourse-strive to trig- ger availability cascades likely to advance their agendas. Their availability campaigns may yield social benefits, but sometimes they bring harm, which suggests a need for safeguards. Focusing on the role of mass pressures in the regulation of risk associated with production, consumption, and the environ- ment, Professors Timur Kuran and Cass R. Sunstein analyze availability cas- cadesandsuggestreformstoalleviatetheirpotentialhazards. Theirproposals include new governmental structures designed to give civil servants better in- sulation against mass demandsfor regulatory change and an easily accessible scientzficdatabasetoreducepeopleSdependenceonpopular (mis)perceptions.