A general equilibrium macroeconomic model based on monopolistic competition is presented. The model exhibits a traditional multiplier in the short run, but due to free entry, the multiplier disappears in the long run. By construction all agents are fully rational. The Keynesian results are a consequence of the assumption of monopolistic competition, which creates a divergence between optimal private behavior and optimal social behavior.

The life cycle/permanent income hypothesis suggests that optimization by consumers should cause marginal utility to approximate a random walk. As a consequence, purchases of nondurable goods should also approximately follow a random walk and purchases of durable goods should approximately follow a white noise process. The univariate processes for nondurables and durables both appear to be random walks, which would confirm the LC/PIH for nondurables and reject it for durables. Adjustment costs and nonseparability between durables and nondurables are then added to the specification of utility. The resulting more general stochastic process is estimated and the data tend to support the existence of nonseparabilty, but not adjustment costs. While forecasts of durables are not fully informationally efficient, they do about as well as do forecasts of nondurables. The behavior of durable consumption purchases is shown to be consistent with the life cycle/permanent income hypothesis.

We examine a variety of models in which the variance of a portfolio's excess return depends on a state variable generated by a first-order Markov process. A model in which the state is known to economic agents is estimated. It suggests that the mean excess return moves inversely with the level of risk. We then estimate a model in which agents are uncertain of the state. The estimates indicate that agents are consistently surprised by high-variance periods, so there is a negative correlation between movements in volatility and in excess returns.