Mapping the efficiency of international scientific collaboration between cities worldwide

The analysis involves 245 cities in which authors produced at least 10,000 publications respectively during 2014–2016. The name of cities (or that of any spatial units between the institution and the country/state level) can be found in the addresses reported by the authors of publications. We focused on only those city-to-city collaborations that produced at least 300 publications during the aforementioned period of analysis (i.e., an average of 100 publications per year). The collaboration matrix of 245 x 245 cities contains a total number of 7,718 international collaboration links that meet the above criteria. Efficiency of the collaboration between each city-dyad corresponds to the ratio of highly cited papers to all papers produced by co-authors affiliated with those cities between 2014 and 2016.