The great entanglement: The contagious capacity of the international banking network just before the 2008 crisis

Systemic risk among the network of international banking groups arises when financial stress threatens to crisscross many national boundaries and expose imperfect international coordination. To assess this risk, we consider three decades of data on the cross-border interbank market. We use Rosvall and Bergstrom's (2008) information theoretic map equation to partition banking groups from 21 countries into modules that reveal the contagious capacity of the network. We show that in the late 1980s four important financial centers formed one large super cluster that was highly contagious in terms of transmission of stress within its ranks, but less contagious on a global scale. But the expansion leading to the 2008 crisis left more transmitting hubs sharing the same total influence as a few large modules had previously. We show that this greater entanglement meant the network was more broadly contagious, and not that risk was more shared. Thus, our analysis contributes to our understanding as to why defaults in US sub-prime mortgages spread quickly through the global financial system.