  We provide an empirical analysis of the network structure of the Austrian
interbank market based on a unique data set of the Oesterreichische
Nationalbank (OeNB). We show that the contract size distribution follows a
power law over more than 3 decades. By using a novel ''dissimilarity'' measure
we find that the interbank network shows a community structure that exactly
mirrors the regional and sectoral organization of the actual Austrian banking
system. The degree distribution of the interbank network shows two different
power law exponents which are one-to-one related to two sub-network structures,
differing in the degree of hierarchical organization. The banking network
moreover shares typical structural features known in numerous complex real
world networks: a low clustering coefficient and a relatively short average
shortest path length. These empirical findings are in marked contrast to
interbank networks that have been analyzed in the theoretical economic and
econo-physics literature.
