Knowledge networks across Europe: which distance matters?

In this paper, we address the manifold nature of knowledge through the analysis of four distinct but complementary phenomena (Internet hyperlinks, EPO co-patent applications, Erasmus students mobility and European research networks) which characterise knowledge as an intrinsic relational structure (directly) connecting people, institutions and (indirectly) regions across five European countries. We study the structure (in terms of density, centralisation, clustering, assortativity, centre-periphery and resilience) of these international knowledge flows through network analysis techniques and we test the influence of geographical distance as opposed to sectoral (based on the industrial distribution of innovative activity) and functional (based on the value of the European technological index) distances in shaping the strength of knowledge relations through a gravitational model. Network Analysis techniques applied to the configuration of international knowledge flows between European regions highlight the existence of a polarised hierarchical structure. By estimating a "gravity equation" model we demonstrate that, far from the claim of the "death of distance", geographic distance is still relevant for determining the structure of inter-regional knowledge flows. Functional and, above all, sectoral distances play also a relevant role suggesting that knowledge flows easier between similar regions (according to their technological level and the industrial distribution of their innovation system).