Leading by Example Among Equals

I examine the factors that determine whether a grassroots social movement reaches the necessary size to achieve its goal. I study a collective action problem where identical individuals who value the common goal sequentially decide whether to join the movement. The model has two key ingredients: (i) The movement is facing a freeriding problem (i.e., while individuals want the movement to succeed, they would rather have others bear the cost of participation) and (ii) The necessary number of members to achieve success is ex-ante unknown but it can be revealed as the movement grows in size. The central insight is that an increase in cost of participation, such as harsher and more likely punishment for members of the movement, can lead to a drastic surge in membership.