Geographical dynamics of knowledge flows: descriptive statistics on inventor network distance and patent citation graphs in the pharmaceutical industry

In the knowledge-based geography of innovation literature, there are two opposing claims on the spatio-temporal pattern in knowledge flows over a technological trajectory. Firstly, after the breakthrough, externalities stimulate agglomeration of specialised firms and thus cause incremental inventions to take place progressively localised. Secondly, after the breakthrough, progressive codification and technological crystallisation facilitates collaboration over greater distances. In this study, forward citation graphs of breakthrough patents are constructed and enriched with locations of inventors. Using these citation graphs, we study claims on co-inventor distances and distances of groups of inventors across citations. We find support for existing claims and alternative spatio-temporal patterns. Notably that, early on in trajectories, inventors generally collaborate mostly locally, yet cite knowledge sources found more remotely. Later on, inventors collaborate over greater distances, yet cite more local sources. Conclusively, there is progressive globalisation of inventor networks, whereby inventors increasingly use local sources in follow-up inventions.