Liquidity Flows in Interbank Networks Fabio Castiglionesiy Mario Eboliz November 2012 Abstract In this paper we model interbank liquidity networks as ‡ow networks. The aim is to compare the ability of di¤erent network structures to cope with the liquidity risk faced by the banks. In particular, we analyze the e¢ ciency of three network structures –star-shaped, complete and incomplete – in transferring liquidity among banks. It turns out that the star-shaped interbank networks achieve the full coverage of liquidity risk with the smallest amount of interbank deposits held by each bank. This implies that star-shaped networks generate the minimum counterparty risk for the banks. Moreover, the star-shaped network is more resilient to systemic risk: the default of one or more banks is less likely to cause the default of the entire system in a star-shaped network than in a complete network. These results provides a rationale of the consistent empirical evidence that interbank network are sparse networks. JEL Classi…cation: D85, G21. Keywords: Interbank Network, Liquidity Coinsurance, Flow Networks. We thank Marco della Seta, Fabio Feriozzi, Ra¤aele Mosca, Wolf Wagner and seminar participants at the Financial Networks Conference 2011 (Geneva), Tilburg University and University of Pescara for helpful comments. The usual disclaimer applies. yCentER, EBC, Department of Finance, Tilburg University. E-mail:
[email protected]. zUniversity of Pescara, Faculty of Economics. E-mail:
[email protected]. 1 1 Introduction One of the main functions provided by banks is liquidity transformation. Banks are there- fore characterized by a maturity mismatch between long-term assets and short-term lia- bilities.