The process of European integration in terms of both functional and territorial expansion spreads far beyond the actual boundaries of the European Union (EU). Various types of integration treaties provide the EU and non-member countries with the means to deepen their bilateral relations. What determines that the European Union and a non-member country agree on a particular integration treaty and not on one of its alternatives? Despite the vital scientific interest and political relevance of the issue, the extant academic literature on the European integration of non-member states remains scarce. In this paper I explain the different degree of integration in the treaties between the EU and non-member countries by the interaction effect of economic and political factors. I in particular argue that the impact of economic interdependence on the degree of integration between the EU and non-member countries is higher when it arises in conjunction with high level of democracy. To assess the theoretical argument, I provide a series of statistical tests, based on the newly compiled data on different types of integration treaties between the EU and 42 non-members in 1990-2010. The gravity model of trade is used to generate a tenable benchmark for economic interdependence. Empirical test supports my argument: Economic interdependence increases the degree of European integration of non-member countries, if they are democracies.
