The basic paradigm of asset pricing is in vibrant flux. The purely rational approach is being subsumed by a broader approach based upon the psychology of investors. In this approach, security expected returns are determined by both risk and misvaluation. This survey sketches a framework for understanding decision biases, evaluates the a priori arguments and the capital market evidence bearing on the importance of investor psychology for security prices, and reviews recent models.

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We propose a general equilibrium model with multiple securities in which investors’ risk preferences and expectations of dividend growth are time varying. While time varying risk preferences induce the standard positive relation between the dividend yield and expected returns, time varying expected dividend growth induces a negative relation between them. These offsetting effects reduce the ability of the dividend yield to forecast returns and eliminate its ability to forecast dividend growth, as observed in the data. The model links the predictability of returns to that of dividend growth, suggesting specific changes to standard linear predictive regressions for both. The model’s predictions are con…rmed empirically.

ABSTRACT In a model with housing collateral, the ratio of housing wealth to human wealth shifts the conditional distribution of asset prices and consumption growth. A decrease in house prices reduces the collateral value of housing, increases household exposure to idiosyncratic risk, and increases the conditional market price of risk. Using aggregate data for the US, we find that a decrease in the ratio of housing wealth to human wealth predicts higher returns on stocks. Conditional on this ratio, the covariance of returns with aggregate risk factors explains eighty percent of the cross-sectional variation in annual size and book-to-market portfolio returns. Keywords: Asset Pricing, Risk Sharing. * First version August 2002. The authors thank Thomas Sargent, Robert Hall, Dirk Krueger, Steven Grenadier, Narayana Kocherlakota, Andrew Abel, Fernando Alvarez, Andrew Atkeson, Patrick Bajari, John Cochrane, Timothey Cogley, Harold Cole, Marco Del Negro, Lars Peter Hansen, John Heaton, Christobal Huneuus, Kenneth Judd, Sydney Ludvigson, Sergei Morozov, Lee Ohanian, Monika Piazzesi, Luigi Pistaferri, Esteban Rossi-Hansberg, Kenneth Singleton, Laura Veldkamp, Pierre-Olivier Weill, Amir Yaron, the editor Robert Stambaugh and an anonymous referee. We also benefited from comments from seminar participants at

We construct a dynamic general equilibrium production economy to explicitly link expected stock returns to firm characteristics such as firm size and the book-to-market ratio. Stock returns in the model are completely characterized by a conditional capital asset pricing model (CAPM). Size and book-to-market are correlated with the true conditional market beta and therefore appear to predict stock returns. The cross-sectional relations between firm characteristics and returns can subsist even after one controls for typical empirical estimates of beta. These findings suggest that the empirical success of size and book-to-market can be consistent with a single-factor conditional CAPM model. We gratefully acknowledge the helpful comments of Andy Abel, Jonathan Berk, Michael

The paper discusses the current state of the behavioral finance literature. I argue that more direct evidence on investors ’ actions and expectations would make existing theories more convincing to outsiders and would help sort among behavioral theories for a given asset pricing phenomenon. Furthermore, evidence on the dependence of a given bias on investor wealth/sophistication would be useful for determining if the bias could be due to (fixed) information or transactions costs or is likely to require a behavioral explanation, and for determining which biases are likely to be most important for asset prices. I analyze a novel data set on investor expectations and actions obtained from UBS PaineWebber/Gallup. The data suggest that, even for high wealth investors, expected returns were high at the peak of the market, many investors thought the market was overvalued but would not correct quickly, and investors ’ beliefs depend strongly on their own investment experience. I then review evidence on the dependence of a series of “irrational ” investor behaviors on investor wealth and conclude that many such behaviors diminish substantially with wealth. As an example of the cost needed to explain a particular type of “irrational”

This paper surveys research on computational agent-based models used in finance. It will concentrate on models where the use of computational tools is critical in the process of crafting models which give insights into the importance and dynamics of investor heterogeneity in many financial settings.

In textbook theory, demand curves for stocks are kept flat by arbitrage between perfect substitutes. Myron Scholes argues in his study of large-block sales that “the market will price assets such that the expected

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