Project Lead: Jihyeon Bae, UW Political Science

Data Science Lead: Curtis Atkisson

Does having a diverse mix of member states make an inter-governmental organization (IGO) more or less cooperative? Scholars have long debated whether regime heterogeneity, especially variation in democracy levels, helps or hinders intergovernmental organizations (IGOs). Yet despite rich theoretical discussions, empirical findings remain mixed. This project addresses that gap by proposing a better way to measure heterogeneity in regime types. Using data on all formal IGOs from 1950 to 2020, we calculate year-by-year variation in member states’ democracy scores. By improving how we quantify regime diversity at the IGO level, we aim to clarify how political differences shape cooperation among countries.

To operationalize heterogeneity, we fit a Beta distribution to the democracy scores of member states in each IGO-year, allowing us to capture both the dispersion and the shape of regime variation more effectively than conventional summary statistics. We also apply a Bayesian framework to estimate the parameters of the Beta distribution, which helps quantify uncertainty and better account for the bounded nature of democracy scores. This approach allows for a more flexible and principled measurement of regime-type heterogeneity across time and institutions.