COLLECTIVE ACTION AND NETWORK STRUCTURE

I develop and analyze a mathematical model describing the relationship between individual contributions to a collective good and the network of social relations that makes these contributions interdependent. St arting from the assumption that actors respond to the contributions of others because of efficacy concerns and norms of fairness, I derive p redictions about the impact of network structure on total contribution s. Network density and size influence collective action outcomes in dr amatically different ways, depending on the structural position of tho se who make unconditional contributions. Moreover these effects are hi ghly nonlinear suggesting that the impact of social ties on collective action may be quite sensitive to mobilization contexts.