Banks' liquidity hoarding can account for a large part of loss propagation which occurs during banking crises. And different institutional environments in interbank markets can also contribute or on the contrary alleviate loss contagion (central clearing houses versus bilateral lending). We explore those issues in an interbank market that features risk averse banks, prone to liquidity hoarding in face of large uncertainty, banks' interconnections and fire sale externalities. We analyze the impact of different institutional arrangements by modeling alternative matching algorithms, namely maximum entropy, closest matching and random matching. Our banking network is well in line with empirical facts as it reproduces dis-assortative behavior, core-periphery structure and low clustering coefficients. We asses contagion through different systemic risk metrics, namely centrality measures, input-output metrics and Shapley values. We find that indeed banks' risk aversion plays an important role and that liquidity hoarding amplifies losses beyond the ones due to interconnections externalities.Given the realm of our model we test whether different regulatory policy can alleviate contagion. We find that liquidity requirements are better fit in addressing the policy trade-off between efficiency (measured as overall investment) and risk (measures by systemic risk metrics).
Bank Networks: Contagion, Systemic Risk and Prudential Policy
January 2015
AbstractWe present a network model of the interbank market in which optimizing risk averse banks lend to each other and invest in non-liquid assets. Market clearing takes place through a tâton-nement process which yields the equilibrium price, while traded quantities are determined by means of a matching algorithm. We compare three alternative matching algorithms: maximum entropy, closest matching and random matching. Contagion occurs through liquidity hoarding, interbank interlinkages and fire sale externalities. The resulting network configurations exhibits a core-periphery structure, dis-assortative behavior and low clustering coefficient. We measure systemic importance by means of network centrality and input-output metrics and the contribution of systemic risk by means of Shapley values. Within this framework we analyze the effects of prudential policies on the stability/efficiency trade-off. Liquidity requirements unequivocally decrease systemic risk but at the cost of lower efficiency (measured by aggregate investment in non-liquid assets); equity requirements tend to reduce risk (hence increase stability) without reducing significantly overall investment.