Exploring the changing geographical pattern of international scientific collaborations through the prism of cities

Science is becoming more and more international breaking down walls in its’ pursuit for high impact. Despite geographical location and distance are still standing as major barriers for scientific collaboration, little is known whether high impact collaborations are similarly constrained by geography like collaborations with an average impact. To address this question, we analyze Web of Science data on international collaboration between global leader cities in science production. We report increasing intensity of international city-city collaboration and find that average distance of collaboration of the strongest connections has slightly increased but distance-decay has remained stable over the last three decades. However, high impact collaborations span large distances by following similar distance decay. This finding suggests that a larger geographical reach of research collaboration should be aimed for to support high impact science. The creation of European Research Area was effective action that has deepened of intracontinental research collaborations and the position of the European Union (EU) in global science. Yet, our results provide new evidence that global scientific leaders are not collaborative enough in carrying out their big science projects.