Systemic risk, financial contagion and financial fragility

Although it is hard to arrive at a widely accepted definition for Systemic Risk; it is generally acknowledged that it is the risk of the occurrence of an event that threatens the well functioning of the system of interest (financial, payments, banking, etc.) sometimes to the point of making its operation impossible. We model systemic risk with two main components: a random shock that weakens one or more financial institutions and a transmission mechanism which transmits and possibly exacerbates such negative effects to the rest of the system. Our model could be conceptually represented by a network already described in previous works. In this work we show how is possible to estimate the distribution of losses for the banking system with our model. Additionally, we show how it is possible to separate the distribution of losses into two components: the losses incurred by the initial shock and the losses resulting from the contagion process. Finally, once the distribution is estimated, we can derive standard risk measures for the system as a whole. Another important contribution of this work is that we can follow the evolution of certain risk measures like the expected loss or the CVaR in order to evaluate if the system is becoming more or less risky, in fact, more or less fragile. Additionally, we can decompose the distribution of losses of the whole banking system into the systemic and the contagion elements and we can determine if the system is more prone to experience contagious difficulties during a certain period of time.