Conditional Diffusion: How Economic Complexity and Democratic Institutions Shape Regional Organizations’ World Polity Adoption

Abstract Although regional organizations (ROs) are systematically embedded in the World Polity, they do not exhibit increasing institutional similarity over time. We advance a theoretical framework in which the extent of World Polity-induced convergence is conditioned by ROs’ democratic composition and economic complexity. Drawing on a dyadic similarity index of 66 ROs’ agreement designs spanning 1972 to 2014, we find robust support for this theory. Three findings emerge. First, diffusion is asymmetric: it is driven primarily by the adopting RO rather than the referenced RO whose designs are being emulated. Second, among adopting ROs, greater democratic membership amplifies World Polity-induced similarity, while greater economic complexity attenuates it, as economically complex ROs customize designs to meet functional requirements rather than adopting global templates wholesale. Third, referenced ROs with more democratic or economically complex members develop more sophisticated designs that present higher barriers to emulation. These asymmetric dynamics account for the persistently low levels of institutional similarity despite pervasive World Polity influence. Constituting the first systematic empirical test of World Polity theory as applied to ROs, our findings reveal that sociological and rationalist logics operate simultaneously and in tension, fundamentally revising how scholars should understand the scope conditions of World Polity influence.