Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
How does a citizen’s decision to participate in political activism depend on the participation of others? We conduct a nationwide natural field experiment in collaboration with a major European party during a recent national election. In a party survey, we randomly provide canvassers with true information about the canvassing intentions of their peers. When learning that more peers participate in canvassing than previously believed, canvassers significantly reduce both their canvassing intentions and behaviour. An additional survey among party supporters underscores the importance of free-riding motives and reveals that there is strong heterogeneity in motives underlying supporters’ behavioural responses.