Fig. 3

Above: The core-periphery profile of the unweighted and weighted WTN in three biennial periods. The unweighted curves are closer to the profile of the complete (all-to-all) network (blue diagonal line), denoting smaller centralization. The weighted curves are closer to the profile of the star network (red angled line), revealing much higher centralization. Below: The time pattern of the weighted coreness \(c_i\) for a sample of selected countries. Only very few countries are part of the core (conventionally defined by \(c_i>0.5\)) for all or most of the time period (they are USA, DEU, JPN, GBR, FRA, ITA). China displays the most dramatic increase and enters the core of the WTN in 2002–2003