Group bargaining: A model of international treaty ratification

We consider non-cooperative bargaining over a fixed surplus between two groups that may differ in size and the supermajority threshold they employ for within-group ratification. We find that total allocation to a group does not depend on group size and increases with the supermajority threshold. We use the Gini coefficient to study within-group inequality as an outcome of interest and find that inequality increases with group size and decreases with the supermajority threshold. Finally, we study delegation by concentrating the ability to influence proposals within a subset of group members. Delegation to a subgroup decreases the group's total allocation because non-delegates accept lower allocations. Inequality is higher if delegation is employed, and it is decreasing in the size of the delegate committee.