Journal of Statistical Physics

, Volume 151, Issue 3–4, pp 765–783 | Cite as

How Big Is Too Big? Critical Shocks for Systemic Failure Cascades

  • Claudio J. Tessone
  • Antonios Garas
  • Beniamino Guerra
  • Frank SchweitzerEmail author


External or internal shocks may lead to the collapse of a system consisting of many agents. If the shock hits only one agent initially and causes it to fail, this can induce a cascade of failures among neighboring agents. Several critical constellations determine whether this cascade affects the system in part or as a whole which, in the second case, leads to systemic risk. We investigate the critical parameters for such cascades in a simple model, where agents are characterized by an individual threshold θ i determining their capacity to handle a load αθ i with 1−α being their safety margin. If agents fail, they redistribute their load equally to K neighboring agents in a regular network. For three different threshold distributions P(θ), we derive analytical results for the size of the cascade, X(t), which is regarded as a measure of systemic risk, and the time when it stops. We focus on two different regimes, (i) EEE, an external extreme event where the size of the shock is of the order of the total capacity of the network, and (ii) RIE, a random internal event where the size of the shock is of the order of the capacity of an agent. We find that even for large extreme events that exceed the capacity of the network finite cascades are still possible, if a power-law threshold distribution is assumed. On the other hand, even small random fluctuations may lead to full cascades if critical conditions are met. Most importantly, we demonstrate that the size of the “big” shock is not the problem, as the systemic risk only varies slightly for changes in the number of initially failing agents, the safety margin and the threshold distribution, which further gives hints on how to reduce systemic risk.


Systemic risk Cascading dynamics 



This work was supported by the Swiss National Science Foundation through grants 100014_126865 and CR12I1-127000.


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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • Claudio J. Tessone
    • 1
  • Antonios Garas
    • 1
  • Beniamino Guerra
    • 1
  • Frank Schweitzer
    • 1
    Email author
  1. 1.Chair of Systems DesignETH ZurichZurichSwitzerland

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