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α: calibrated so average coauthorship-adjusted count equals average raw count
We study the effects of varying individual pivotality and endogenous group entry on the selfishness of group decisions. Selfish choices by groups are often linked to the possibility of diffusing responsibility; the moral costs of these decisions appear smaller when individual pivotality is reduced. Our experimental design explores unanimity voting under distinct defaults to identify this effect. In exogenously formed groups we find evidence of responsibility diffusion, but this diminishes with repetition. Our results also demonstrate the role of self-selection in generating differences in group behaviour depending on individual pivotality. Driven by a heterogeneous selection pattern, endogenous group formation amplifies the effects of a change in pivotality. Some people actively seek an environment to diffuse responsibility, while others join groups to promote pro-social behaviour.