This paper investigates the feasibility of a monetary policy aimed at pegging the nominal rate of interest. It shows that under general conditions such a policy would produce the well-known cumulative process, despite the fact that there exists a well-behaved rational expectations equilibrium with no tendency for inflation to accelerate or decelerate. The cumulative process shows up as the failure of learning to converge to rational expectations. Specifically, the paper shows, first in a conventional IS-LM model with an expectations-augmented Phillips curve and then in a micro-based finance constraint model, that if people follow any learning rule based on experience that satisfies a weak condition, then the sequence of temporary equilibria under a policy of interest pegging cannot converge. The nonconvergent path that will be observed accords with the familiar cumulative process, in that inflation accelerates if the market rate of interest has been pegged below the natural rate.

This paper investigates the feasibility of a monetary policy aimed at pegging the nominal rate of interest. It shows that under general conditions such a policy would produce the well-known cumulative process, despite the fact that there exists a well-behaved rational expectations equilibrium with no tendency for inflation to accelerate or decelerate. The cumulative process shows up as the failure of learning to converge to rational expectations. Specifically, the paper shows, first in a conventional IS-LM model with an expectations-augmented Phillips curve and then in a micro-based finance constraint model, that if people follow any learning rule based on experience that satisfies a weak condition, then the sequence of temporary equilibria under a policy of interest pegging cannot converge. The nonconvergent path that will be observed accords with the familiar cumulative process, in that inflation accelerates if the market rate of interest has been pegged below the natural rate.

This paper constructs a stationary rational-expectations equilibrium in which an extraneous random variable, called animal spirits, causes fluctuations in unemployment. The model assumes costly matching in the labor market and a thin-market externality in the output market that makes the profitability of hiring depend positively on the number of firms hiring. The equilibrium does not rely on any effect of expected inflation on labor supply. It is also stable under learning; Bayesian updating induces convergence to the equilibrium with positive probability even if people start with no definite belief that animal spirits affect the profitability of hiring.

This paper develops a model based on Schumpeter's process of creative destruction. It departs from existing models of endogenous growth in emphasizing obsolescence of old technologies induced by the accumulation of knowledge and the resulting process or industrial innovations. This has both positive and normative implications for growth. In positive terms, the prospect of a high level of research in the future can deter research today by threatening the fruits of that research with rapid obsolescence. In normative terms, obsolescence creates a negative externality from innovations, and hence a tendency for laissez-faire economies to generate too many innovations, i.e too much growth. This business-stealing effect is partly compensated by the fact that innovations tend to be too small under laissez-faire. The model possesses a unique balanced growth equilibrium in which the log of GNP follows a random walk with drift. The size of the drift is the average growth rate of the economy and it is endogenous to the model ; in particular it depends on the size and likelihood of innovations resulting from research and also on the degree of market power available to an innovator.