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The interbank market is considered one of the most important channels 6 of contagion. Its network representation, where banks and claims/obligations are 7 represented by nodes and links (respectively), has received a lot of attention in 8 the recent theoretical and empirical literature, for assessing systemic risk and 9 identifying systematically important financial institutions. Different types of links, 10 for example in terms of maturity and collateralization of the claim/obligation, can 11 be established between financial institutions. Therefore a natural representation of 12 the interbank structure which takes into account more features of the market, is 13 a multiplex, where each layer is associated with a type of link. In this paper we 14 review the empirical structure of the multiplex and the theoretical consequences of 15 this representation. We also investigate the betweenness and eigenvector centrality 16 of a bank in the network, comparing its centrality properties across different layers 17 and with Maximum Entropy null models.

The interbank market is considered one of the most important channels of contagion. Its network representation, where banks and claims/obligations are represented by nodes and links (respectively), has received a lot of attention in the recent theoretical and empirical literature, for assessing systemic risk and identifying systematically important financial institutions. Different types of links, for example in terms of maturity and collateralization of the claim/obligation, can be established between financial institutions. Therefore a natural representation of the interbank structure which takes into account more features of the market, is a multiplex, where each layer is associated with a type of link. In this paper we review the empirical structure of the multiplex and the theoretical consequences of this representation. We also investigate the betweenness and eigenvector centrality of a bank in the network, comparing its centrality properties across different layers and with Maximum Entropy null models., To appear in the book "Interconnected Networks", A. Garas e F. Schweitzer (eds.), Springer Complexity Series

This special issue of Quantitative Finance collects eight papers on the relation between interlinkages and systemic risk. The papers cover several types of interlinkages and follow different approaches, from agent-based modelling to empirical investigation of large and sometimes confidential data. The special issue collects some of the contributions presented at the international workshop‘Interlinkages and systemic risk ’ , which took place in Ancona (Italy) on 4 – 5 July 2013. The workshop, organized within the research project‘. New tools in the credit network modeling with agents ’ heterogeneity ’ funded by the Institute for New Economic Thinking, was attended by a balanced mix of scholars from academia and economists from central banks and regulatory authorities.

The interbank market has a natural multiplex network representation. We employ a unique database of supervisory reports of Italian banks to the Banca d'Italia that includes all bilateral exposures broken down by maturity and by the secured and unsecured nature of the contract. We find that layers have different topological properties and persistence over time. The presence of a link in a layer is not a good predictor of the presence of the same link in other layers. Maximum entropy models reveal different unexpected substructures, such as network motifs, in different layers. Using the total interbank network or focusing on a specific layer as representative of the other layers provides a poor representation of interlinkages in the interbank market and could lead to biased estimation of systemic risk., 41 pages, 8 figures, 10 tables