The optimal liquidity principle with restricted borrowing

A model is presented to characterise the (optimal) demand for cash balances in deregulated markets. After the model of James Tobin, 1958, net balances are determined in order to maximise the expected return of a certain portfolio combining risk and capital. Unlike the model of Tobin, however, the price of the underlying exposures are established in actuarial terms. Within this setting, the monetary equilibrium determines the rate at which a unit of capital is exchange by a unit of exposure to risk, or equivalently, it determines the market price of risk. In a Gaussian setting, such a price is expressed as a mean-to-volatility ratio and can then be regarded as an alternative measure to the Sharpe ratio. The effects of credit and monetary flows on money and security markets can be precisely described on these grounds. An alternative framework for the analysis of monetary policy is thus provided.