Collective Action Cascades: An Informational Rationale for the Power in Numbers

Self‐interested individuals pursue their goals rationally taking into account the constraints imposed by their environment and best‐responding to the strategic behavior of other individuals: when applied to collective action, economic theory predicts undersupply. Meanwhile, the behavior of masses of people is described as excitable, emotional, irrational, suggestible, hypnotic, disorderly, and unpredictable: in practice, it seems, collective action is oversupplied, and erratically so. The contagious and volatile dynamics of collective action appear to defy rationalization. I conceptualize a social movement as a dynamic informational cascade. Turbulencies emerge endogenously from rational individual behavior. Disorderly mass behavior is a by‐product of a powerful decentralized mechanism of information aggregation.