Larger groups may alleviate collective action problems

This paper shows how larger group size can enhance punishing behavior in social dilemmas and hence support higher levels of cooperation. This occurs when agents can punish fellow group members who violate cooperative norms. Unlike existing approaches that focus on decentralized punishment, I view punishment to be a collective activity and show that pun- ishers can ?divide and conquer?defectors more e¢´ectively as the size of the group increases. To describe the punishment activities more precisely I develop a con?ict model which gener- alizes Lanchester?s equations - equations which describe the time evolution of the strengths of two competing armies.