Zusammenfassung
The scope of financial systemic risk research encompasses a wide range of
channels and effects, including asset correlation shocks, default contagion,
illiquidity contagion, and asset firesales. For example, insolvency of a given
bank will create a shock to the asset side of the balance sheet of each of its
creditor banks and under some circumstances, such "downstream" shocks can cause
further insolvencies that may build up to create what is called an insolvency
or default cascade. On the other hand, funding illiquidity that hits a given
bank will create a shock to the liability side of the balance sheet of each of
its debtor banks. Under some circumstances, such üpstream" shocks can cause
illiquidity in further banks that may build up to create an illiquidity
cascade. This paper introduces a deliberately simplified financial network
model that combines the default and liquidity stress mechanisms into a "double
cascade mapping". The progress and eventual result of the crisis is obtained by
iterating this mapping to its fixed point. Unlike simpler models, this model
can therefore quantify how illiquidity or default of one bank influences the
eventual overall level of liquidity stress and default in the system.
Large-network asymptotic cascade mapping formulas are derived that can be used
for efficient network computations of the double cascade. Numerical experiments
then demonstrate that these asymptotic formulas agree qualitatively with Monte
Carlo results for large finite networks, and quantitatively except when the
initial system is placed in an exceptional "knife-edge" configuration. The
experiments clearly support the main conclusion that in the absence of fire
sales, the average eventual level of defaults in a financial network is
negatively related to the strength of banks' liquidity stress response and the
eventual level of stress in the network.
Nutzer