  We test the hypothesis that protest participation decisions in an adult
population of potential climate protesters are interdependent. Subjects
(n=1,510) from the four largest German cities were recruited two weeks before
protest date. We measured participation (ex post) and beliefs about the other
subjects' participation (ex ante) in an online survey, used a randomized
informational intervention to induce exogenous variance in beliefs, and
estimated the causal effect of a change in belief on the probability of
participation using a control function approach. Participation decisions are
found to be strategic substitutes: a one percentage-point increase of belief
causes a .67 percentage-point decrease in the probability of participation in
the average subject.
