Fig. 3
From: Quantifying the diaspora of knowledge in the last century
Incoming and outgoing flows from and to knowledge areas across time. Immigration (panel a) and emigration (panel b) index (see Eq. 2 and 3) of each area calculated for each temporal snapshot. Here, 0 indicates that the incoming (outgoing) flow of immigrating (emigrating) authors is negligible with respect to the existing authors population in the area, and 1 that the existing population is negligible with respect to the incoming (outgoing) flow of immigrating (emigrating) authors. Size of circles are proportional to the volume of authors in each area, and areas are ordered according to their overall volume over time. c Median sink (left, red boxes) and source (right, blue boxes) index (see Eq. 4 and 5) calculated for each area. Both range from 0 – indicating areas where the incoming (outgoing) flow of authors is negligible with respect to the overall incoming (outgoing) flow – to 1 – characterizing areas where the incoming (outgoing) flow of authors dominates the overall incoming (outgoing) flow. White dots indicate the difference between the two indicators, to better put in evidence the one with higher value