International governance institutions do not exist in isolation from each other. Frequently, they overlap both in regard to their membership and their respective issue-area. Thus, governance effects emerge from institutional complexes made up of a number of separately established institutions. Moreover, international institutions affect each others’ normative development and performance. Institutional fragmentation and the increasing institutional density within the international system accelerate interaction among institutions.

The project on institutional complexes was driven by two objectives.

First, a number of causal mechanisms were to be identified that were capable of explaining how one international institution can affect another international institution.

Secondly, intstitutional complexes were to be examined as systems of institutions that produce, over time, systemic effects. Here, the project was particularly concerned with the division of labour among the elemental institutions.