Fig. 3
Minimum spanning tree of the similarity matrix associated with the trading activity of clusters for year 2005. Each cluster is labeled by a number. Symbols in colors indicate the over-expression of one or more category of investors. Colors refer to the different categories as follows: non-financial corporations (green), financial and insurance corporations (red), general governmental organizations (gray), non-profit organizations (yellow), households (cyan), and foreign organizations (brown). The size of each node is proportional to the logarithm of the number of investors that are in the cluster
