The market economy is modeled as a decentralized joint production system. Markets in such an economy require the use of money or credit instruments to facilitate exchange. As a result, market economies are at risk for monetary instability induced by real-side production coordination failure. In particular, economies decentralized via centralized wholesaling markets are subject to precipitous collapses. The most stable monetary system is trade in specie. However, there very likely is a scarcity of specie, which generates inefficiency and discourages production. There is, then, a need for an elastic currency. Bank-issued bills of exchange are a perfectly elastic medium and eliminate the scarcity of specie and its attendant inefficiency, but are a less stable monetary system than is trade in specie. In the trade-off between elasticity and stability, fiduciary currency (or fiduciary deposits) lies between specie and bank-issued bills of exchange.