In so far as the concept of systematic risk is predicated on the Sharpe-Lintner theory of capital market equilibrium [5, 4], the time-horizon of systematic risk must conform with the time-horizon of market equilibrium. Since it has been suggested that market equilibrium is instantaneous [3, p. 188], it would follow that systematic risk should also be instantaneous. This paper is, therefore, concerned with the evaluation and measurement of instantaneous risk. Although Jensen [3] has made a similar attempt in a much larger study, we have reason to believe it is not satisfactory. We shall then begin in Section I by discussing Jensen's approach to the horizon problem. In Section II, an alternative procedure of evaluating systematic risk is suggested. Section III concludes the paper by comparing estimates of instantaneous risks based upon weekly returns of 30 Dow-Jones stocks. The motivation behind the paper is obvious. A correct formulation of instantaneous systematic risk is not only a logical extension of the capital market equilibrium theory but is also a yardstick for measuring portfolio performance in terms of risk and return.

Ex ante predictions of the riskiness of returns on common stocks — or, in more general terms, predictions of the probability distribution of returns — can be based on fundamental (accounting) data for the firm and also on the previous history of stock prices. In this article, we attempt to combine both sources of information to provide efficient predictions of the probability distribution of returns. We predict two parameters of the distribution of returns for each security in each year: the response to the overall market return (β), and the variance of the part of risk, specific to the security, that is uncorrelated with the market return. A cross section of time series data on returns and accounting variables, taken primarily from the Compustat tape, is used. Several recent developments in statistical methodology are applied.

This study deals with behavioral assumptions that necessarily underlie the theory of asset valuation. Recognized logical and empirical implausibilities associated with the particular set of assumptions that provides the underpinnings of much currently espoused asset theory are reviewed. A valuation model based on a more realistic set of behavioral assumptions is then proposed and tested empirically.

In their present paper. Professors Cheng and Deets (hereafter C-D) attempt to derive a measure of instantaneous systematic risk for securities and portfolios which is consistent with the Sharpe-Lintner-Mossin capital asset pricing model when the true market horizon is infinitesimally short. In so doing, they assert that Jensen's resolution of the horizon problem for such a market horizon is incorrect. In the comments which follow, I shall attempt first to indicate explicitly the causes for the differences in the Jensen and C–D results, and second, to evaluate their relative merits.

Major points covered by Paul H. Cootner in his discussion of “The Prediction of Systematic and Specific Risk in Common Stocks” by Barr Rosenberg and Walter McKibben have been incorporated by the authors in the revised version of their paper.

Professor Huntsman's paper is a welcome addition to the growing literature on portfolio theory. Traditional mean-variance analysis, in spite of its obvious simplicity and its ability to explain portfolio diversification, has come under increasing attack, both for the theoretical weaknesses underlying the technique and for its failure to recognize that investors manifestly prefer returns that are positively skewed to those that are not.

It has been a pleasure and a worthwhile experience to serve as President of the Western Finance Association (WFA) and to have had the opportunity to work with its officers and committee chairmen over this past year. In the brief history of the Association, our organization has come a long way in becoming firmly established due to the strong interest of its members and to the dedicated support of its officers and working committees. I wish to take a few moments to publicly acknowledge the services of a few who have given vital support to the activities of the Association during the past twelve months.