The EU has a decisive influence on other regional associations of states

States outside Europe also cooperate on a regional level and the cooperation is often institutionally organised. Four such associations are the Southern African Development Community, Mercosur (South America), the Association of Southeast Asian Nations and the North American Free Trade Agreement. In his study, which employs both quantitative and qualitative methods, Lenz examines how and under what conditions the EU shapes the emergence of institutions in these organisations. This shaping occurs through diffusion - just as a drop of ink diffuses in a glass of water - i.e. through the spread of political ideas.

The EU is a successful pioneer among associations of states. As such, it influences national preferences about how other governments want to set up their regional institutions ("institutional preferences"). The Union does this both actively, by working closely with other associations of states, and passively, by creating successful institutions that invite emulation. "My main argument," Lenz explains, "is that the existence of the EU has made a discernible and substantial difference in the institutional design of state associations in other parts of the world - conversely, in the absence of the EU, they would be significantly less institutionalised." This has been repeatedly asserted in previous empirical research, but not systematically investigated. Political science theories, moreover, have largely ignored this diffusion phenomenon.

Hence, while the EU is a model and point of reference for other associations of states, this does not make it unique: Lenz demonstrates that some have succeeded in building institutions even faster than the EU and that the degree of institutionalisation of EU and some non-EU organisations is converging.