Screening Out Risk: IGOs, Member State Selection, and Interstate Conflict, 1951–2000

Do intergovernmental organizations (IGOs) screen out conflict-prone states? We argue that IGOs have incentives to guard against admitting new members that pose significant security risks. Using a data set 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—also prove particularly selective and sensitive to risk.