  To identify emerging interdependencies between traded stocks we investigate
the behavior of the stocks of FTSE 100 companies in the period 2000-2015, by
looking at daily stock values. Exploiting the power of information theoretical
measures to extract direct influences between multiple time series, we compute
the information flow across stock values to identify several different regimes.
While small information flows is detected in most of the period, a dramatically
different situation occurs in the proximity of global financial crises, where
stock values exhibit strong and substantial interdependence for a prolonged
period. This behavior is consistent with what one would generally expect from a
complex system near criticality in physical systems, showing the long lasting
effects of crashes on stock markets.
