Screening out Risk: IGOs, Member State Selection, and Interstate Conflict

Do intergovernmental organizations (IGOs) screen out conflict-prone states? We argue that IGOs have incentives to guard against admitting new members that pose high levels of security risk—understood as the state’s ex ante probability of involvement in militarized interstate conflict. We outline and test three mechanisms through which security risk undermines IGO functioning. Using a dataset based on state-IGO pairings, we find clear evidence of screening: as security risk increases, the probability of IGO membership declines. Our findings underscore the importance of accounting for possible selection bias when studying the effects of IGO membership on conflict. Indeed, the types of IGOs sometimes found to be most effective at promoting peace—namely, highly institutionalized organizations and those with a security mandate—are also the ones particularly selective and sensitive to risk.