Financial contagion is modeled as an equilibrium phenomenon. Because liquidity preference shocks are imperfectly correlated across regions, banks hold inter-regional claims on other banks to provide insurance against liquidity preference shocks. When there is no aggregate uncertainty, the first-best allocation of risk sharing can be achieved. However, this arrangement is financially fragile. A small liquidity preference shock in one region can spread by contagion throughout the economy. The possibility of contagion depends strongly on the completeness of the structure of interregional claims. Complete claims structures are shown to be more robust than incomplete structures.

In an overlapping generations economy with (incomplete) financial markets but no intermediaries, there is underinvestment in safe assets. In an economy with intermediaries and no financial markets, accumulating reserves of save assets allows returns to be smoothed, nondiversifiable risk to be eliminated, and an ex ante Pareto improvement compared to the allocation in the market equilibrium to be achieved. In a mixed financial system, however, competition from financial markets constrains intermediaries so that they perform no better than markets alone.