Financial intermediaries and markets

A complex financial system comprises both financial markets and financial interme-diaries. We distinguish financial intermediaries according to whether they issue com-plete contingent contracts or incomplete contracts. Intermediaries such as banks that issue incomplete contracts, e.g., demand deposits, are subject to runs, but this does not imply a market failure. A sophisticated financial system—a system with complete markets for aggregate risk and limited market participation—is incentive-efficient, if the intermediaries issue complete contingent contracts, or else constrained-efficient, if they issue incomplete contracts. We argue that there may be a role for regulating liquidity provision in an economy in which markets for aggregate risks are incomplete