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This paper investigates the performance of efficient portfolios in a financial market with heterogeneous investors including rational traders, noise traders, and chartists. A generalization of the security market line result states that, regardless of the diversity of beliefs, the portfolios of rational investors with mean-variance preferences are mean-variance efficient in the sense of classical CAPM. We show that, depending on the noise traders' behavior, the performance of efficient portfolios when measured by empirical Sharpe ratios can be dominated. Empirical Sharpe ratios may thus be inappropriate indicators for efficient portfolios. r 2004 Elsevier B.V. All rights reserved. JEL classification: G11; O16

The paper studies the nature of expectations formation rules for deterministic economic laws with an expectations feedback within the framework of dynamical systems theory. In such systems, the expectations formation rules, called predictors, have a dominant influence. The concept of a perfect predictor, which generates perfect-foresight orbits, is proposed and analyzed. Necessary and sufficient conditions are given for which local as well as global perfect foresight is possible. The concept is illustrated for the general linear model as well as for models of the cobweb type. For the standard overlapping generations model of economic growth, the existence of perfect predictions depends strongly on the savings behavior of the agents and on the technology.

This paper studies the question to what extent premia for macroeconomic risks in banking are sufficient to avoid banking crises. We investigate a competitive banking system embedded in an overlapping generation model subject to repeated macroeconomic shocks. We show that even if banks fully incorporate macroeconomic risks in their pricing of loans, a banking system may enter bankruptcy with a probability of one. A major cause for this default is that risk premia of a competitive banking system may become too small if the capital base is low.

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