The number of investors in Nokia stocks during the period 1998–2002 and the change in the number of investors across the six-month time windows.

<p>(a) The number of investors <i>N</i>_>(<i>T</i>) who traded the Nokia stock at least on <i>T</i> different days during the whole time period 1998–2002 (i.e., a non-normalized complementary cumulative distribution). (b) The evolution of the number of investors trading Nokia in the six-month time windows for households, non-financial institutions, and financial institutions. The numbers of investors in each category |<i>n</i>_<i>t</i>| vary widely across categories, and they are normalized by the average numbers of investors in the full time period 〈|<i>n</i>_<i>t</i>|〉. (c) The change in the number of investors is measured using the Jaccard coefficient for different investor categories. The value of <i>J</i>(<i>t</i>) is higher (lower) the more (less) similar the consecutive networks are in terms of nodes in them (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0198807#pone.0198807.e001" target="_blank">Eq 1</a>). Results for each time window in panels (b) and (c) are plotted at the end of the window. That is, each point is estimated with data over the previous 126 trading days (6 months). The estimation windows are rolling by one month, and the resulting points are joined by solid lines. In panels (b) and (c), the green dotted vertical line in the figures represents the highest stock price of Nokia in the sample period, and the blue curves (with axis on the right) represent the Nokia stock price. In all panels, the lime-green curve corresponds to financial institutions, the cyan curve to households, and the orange curve to non-financial institutions.