Overlapping generations models with or without production or a portfolio demand for money display a fundamental indeterminacy. Expectations matter; and they are not, in the short run, constrained by the hypotheses of agent optimization, rational expectations, and market clearing. No short run policy analysis is possible without some explicit understanding of how agents expect the economy to respond to the policy. In this framework of perfect foresight and market clearing prices, it is possible to make Keynesian assumptions about the rigidity of money wages and the exogeneity of “animal spirits” of investors, to use the standard IS-LM apparatus, and to derive Keynesian conclusions about the short run effectiveness of policy. Alternatively, starting from different but no less rational expectations, one can derive the “new classical” neutrality propositions.

A general equilibrium model of imperfectly competitive financial intermediaries is constructed and used to study the effects of some standard policy experiments. One-time increases in the growth rate and in the level of the stock of money have non-neutral (and sometimes surprising) effects on interest rates, the quantity of intermediated borrowing and lending, the number of intermediary firms, inflation and the price level. Optimal government macroeconomic policy is shown to reflect a tradeoff between public sector frictions and the capital market distortion created by increasing returns to scale and imperfect competition in private intermediation.