Fig. 4: The proportions of publications from each country across all periods and in three different decades.

The percentage of publications from each country is represented by different colors. Dark green represents a proportion of 0%–1%, light green represents 1%–3%, yellow represents 3%–10%, orange represents 10%–20%, and red represents 20%–100%. (a) It shows the proportion of publications from each country across all periods. The proportion of publications in three different decades is displayed in (b), (c) and (d).