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This article summarizes the new Correlates of War 2 International Governmental Organizations (IGOs) data. The data in the Correlates of War IGO data sets capture state memberships in the network of international governmental organizations. The expanded version 2.0 updates the original Wallace and Singer (1970) data set to provide membership information from1964 to 2001. Following a brief review of the literature pertaining to IGOs and world politics, we provide descriptions of all three versions of the data (country-year, IGO-year, and joint dyadic membership), discuss coding rules and subsequent changes to the data, and present graphical representations of changes in the network of IGOs over time using all three versions of the data.
Pevehouse et al. (Thu,) studied this question.