Fig. 4
a The global collaboration network constructed for data between 2015–2018. The algorithm ForceAtlas is used to layout the network, with edges above a 0.5 edge-weight threshold shown. Node sizes are scaled according to the total number of publications during this period, labeled with the ISO2 code corresponding to each country, and coloured according to geographical regions. b–d show analogous networks constructed for periods 1970–1974, 1985–1989, and 2000–2004. Finally, e displays mean edge weights between the five continents in the form of adjacency matrices. We observe a concentration of edge weights within regions, as seen by the shaded diagonal entries, particularly from 2000. Colours correspond to the same continent in each plot