The networked peace: Intergovernmental organizations and international conflict

Existing work has shown that membership in intergovernmental organizations (IGOs) can, among other outcomes, reduce conflict, promote democratization, and shape crisis bargaining. The traditional approach to studying how IGOs can reduce conflict has focused on the effects of dyads' direct ties to IGOs. In doing so, these analyses use fairly simple counts of the number of IGOs to which the states in each dyad share membership. We argue that this approach is too narrow; we instead consider the effects of higher-order groupings within the IGO network, which we call IGO clusters. Within these IGO clusters, states share relatively many IGO connections with each other, both directly and through indirect links through third parties, fourth parties, and so on. The effects of indirect IGO ties are especially important within such structures. We use a modularity maximization approach to detect clusters within the IGO network. We find robust empirical support for our hypothesis that the pacifying effect of IGO membership stems from the extent to which pairs of states are more deeply embedded within the wider IGO network. Indeed, we find that once we account for states' shared membership in clusters of IGOs, the simpler dyadic measure of shared IGO membership no longer shows evidence of a conflict-inhibiting effect.