Multipolar or multiplex? Interaction capacity, global cooperation and world order

Abstract This article uses a new concept—multiplexity, rather than multipolarity or liberal hegemony—to describe and analyse the changing world order. Instead of conventional measures like economic or military power, it uses ‘interaction capacity’ among states, or the relative ability of nations to exercise leadership and organize cooperation as the key world order measure. Using a new dataset composed of post-Second World War treaties to measure interaction capacity, it finds the world order changing from United States leadership, toward a more de-centered, pluralistically led (multiplex) world—a decline in the relative importance of great powers, an increase in the interaction capacity of middle and small powers, and the significance of clusters of cooperation among nations that are not necessarily geographically close to each other. We conclude that, while leadership in global cooperation is increasingly pluralized along actors and issue areas, it is not collapsing or becoming overly transactional. These findings should guide debates on the future of world order and reform of international institutions. While policy makers must prepare for a transition from the unipolar moment and the rise of non-western nations, they should not succumb to undue pessimism about the collapse of global cooperation, which is underpinned by long-term dynamics of interaction capacity among nations.