Portfolio inefficiency and the cross-section of expected returns

Article Abstract:

The Capital Asset Pricing Model implies that (i) the market portfolio is efficient and (ii) expected returns are linearly related to betas. Many do not view these implications as separate, since either implies the other, but we demonstrate that either can hold nearly perfectly while the other fails grossly. If the index portfolio is inefficient, then the coefficients and R(super)2 from an ordinary least squares regression of expected returns on betas can equal essentially any values and bear no relation to the index portfolio's mean-variance location. That location does determine the outcome of a mean-beta regression fitted by generalized least squares. (Reprinted by permission of the publisher.)

Author: Stambaugh, Robert F., Kandel, Shmuel
Investments, Capital assets pricing model, Capital asset pricing model

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Tests of asset pricing with time-varying expected risk premiums and market betas

Article Abstract:

Tests of asset-pricing models are developed that allow expected risk premiums and market betas to vary over time. These tests exploit the relation between expected excess returns and current market values. Using weekly data for 1963 through 1982 on ten common stock portfolios formed according to equity capitalization, a single-risk-premium model is not rejected if the expected premium is time varying and is not constrained to correspond to a market factor. Conditional mean-variance efficiency of a value-weighted stock index is rejected, and the rejection is insensitive to how much variability of expected risk premiums is assumed. (Reprinted by permission of the publisher.)

Author: Stambaugh, Robert F., Ferson, Wayne E., Kandel, Shmuel
Stock-exchange, Stock exchanges

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On the predictability of stock returns: an asset-allocation perspective

Article Abstract:

Sample evidence about the predictability of monthly stock returns is considered from the perspective of a risk-averse Bayesian investor who must allocate funds between stocks and cash. The investor uses the sample evidence to update prior beliefs about the parameters in a regression of stock returns on a set of predictive variables. The regression relation can seem weak when described by usual statistical measures, but the current values of the predictive variables can exert a substantial influence on the investor's portfolio decision, even when the investor's prior beliefs are weighted against predictability. (Reprinted by permission of the publisher.)

Author: Stambaugh, Robert F., Kandel, Shmuel
Analysis, Forecasts and trends, Stock price forecasting

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Subjects list: Research, Portfolio management, Return on investment, Rate of return, Prices and rates, Stocks, Stock prices
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