  We discuss the systemic risk implied by the interbank exposures reconstructed
with the maximum entropy method. The maximum entropy method severely
underestimates the risk of interbank contagion by assuming a fully connected
network, while in reality the structure of the interbank network is sparsely
connected. Here, we formulate an algorithm for sparse network reconstruction,
and we show numerically that it provides a more reliable estimation of the
systemic risk.
