FIGURE 4. Disciplinary strengths in the United States, the 15 European Union nations in the comparator group (EU15), and the United Kingdom.
From the following article:
The scientific impact of nations
David A. King
Nature 430, 311-316(15 July 2004)
doi:10.1038/430311a
The distance from the origin to the data point is proportional to citation share.
