This article summarizes the Correlates of War Intergovernmental Organizations (IGO) Version 3.0 datasets. The new datasets include information about the population of IGOs in the international system and state participation in those formal international institutions from 1816 to 2014. Consistent with Versions 2.0 and 2.3, Version 3.0 of the IGO data comes in three forms: country-year, IGO-year, and joint dyadic membership. This article briefly describes the data collection process and identifies important changes to the dataset before moving to analyze fundamental patterns in the data. Most notable among the changes from earlier versions of the data is the inclusion of annual membership data for the 1815–1964 time period. In addition, we present information about the overall trends in the institutionalization of cooperation at both the global and regional levels, with the latter focusing on the interesting membership dynamics in Asia and Africa. We then track and discuss patterns in state memberships and examine how these changes manifest in the dyadic data. The article concludes with a discussion of how the COW IGO 3.0 data compare to other prominent datasets on state participation in international institutions and highlights some new areas of research that will benefit from the release of the updated IGO membership dataset.
- International organizations