Supplementary information files for: Do intergovernmental organizations have a socialization effect on member state preferences? Evidence from the UN general debate

The question of whether intergovernmental organizations (IGOs) have a socialization effect on member state preferences is central to international relations. However, empirical studies have struggled to separate the socializing effects of IGOs on preferences from the coercion and incentives associated with IGOs that may lead to foreign policy alignment without altering preferences. This article addresses this issue. We adopt a novel approach to measuring state preferences by applying text analytic methods to country statements in the annual United Nations General Debate (UNGD). The absence of interstate coordination with UNGD statements makes them particularly well suited for testing socialization effects on state preferences. We focus on the European Union (EU), enabling us to incorporate the pre-accession period—when states have the strongest incentives for foreign policy alignment—into our analysis. The results of our analysis show that EU membership has a socialization effect that produces preference convergence, controlling for coercion and incentive effects.