UNIVERSITY OF ILLINOIS LIBRARY AT URBANACHAMPAIQN BOOKSTACKS CENTRAL CIRCULATION BOOKSTACKS The person charging this material is re- sponsible for its renewal or its return to the library from which it was borrowed on or before the Latest Date stamped below. You may be charged a minimum fee of $75.00 for each lost boolc. llMft/ mutilation, and underlining of books are reasons for disciplinary action . is used to estimate 6 , a., a , and a . The generalized least squares (GLS) estimated constant component of systematic risk (B) and the GLS estimated a. are calculated as defined in equation (lA); and the asymptotic variance estimators associated with 3 and a. are calculated 2 as defined in equation (15). The least squares estimators for both 2 4 and a are found in equation (9.2). To measure the degree of uncertainty, an index of uncertainty (lOU) is defined following the coefficient of variation concept as: (16) lOUj = %j/|6j!. where a is the estimated population standard deviation associated with the beta coefficient for the jth firm. 6, is the estimated constant component of the beta coefficient for the jth firm. This index 3 2 t X> . was added to test the convergence of beta tendency. How- ever, due to the high degree of multicollinearity, this variable was dropped in the final model. There exists about twenty percent of stocks with negative esti- 2 mated a . As Fabozzi and Francis [1978] pointed out, the restricted GLS emcloying quadratic programming can be used to deal with this kind of problem. This index has been used by Kau and Lee [1977] to measure the de- gree of stability of the density gradient for an urban structure study. -9- provides a criteria for security analysts to decide whether the histori- cal beta coefficient of a firm is an acceptable predictor for the future beta of the firm. The mean and standard deviation of the estimated lOU for 363 firms are 1.209 and 1.671 respectively. It is obvious that the estimated population standard deviation associated with the beta coeffi- cient (a ) can also be used to formulate the interval estimate for a firm's beta coefficient. An index of uncertainty can also be an indi- cator of the marginal benefit of utilizing the multi-index CAPM. As the index approaches zero, the implication is that 3. is an efficient pop- ulation estimate and requires no additional data to estimate the multi- index CAPM. According to the estimates derived in this study, sixty- five percent of the sample firms have o values which are significantly different from zero. This suggests that the residuals associated with these fiinns are not homoscedastic. One hundred five firms (29%) have an estimated a value that is significantly different from zero. This indicates that a significant portion of the sample firms have shifting betas during the period from 1965 to 1975. This result, in addition to 2 the significant a values, could well indicate that a variable mean re- n sponse regression market model better describes the beta coefficient for some firms than does the constant beta and/or pure random beta mod- A els. From the signs of 6. and a^^, it is found that there exists some regression tendency as established earlier by Blume [1975]. This argu- ment is based upon the fact that the estimated value of a is a factor for adjusting the beta coefficient toward unity. In other words, the sign of a. is generally positive when the magnitude of of the estimated beta is less than one, and negative if the magnitude of beta is greater -10- than one. Hence the sign, magnitude, and degree of significance of a. provides information for security analysts to improve their forcasting of future beta coefficients. To investigate the possible success of beta predictions of variable mean response regression model relative to the traditional fixed coeffi- cient regression model, the mean squared error (MSE) technique developed by Mincer and Zarnowitz [1969] as indicated in equation (17) will be used to do empirical analysis. (17) MSE = (\^^-\)' + a~\)^S^l 4. (1-r2,^i.3,)s2^, bias inefficiency random error where 6 . and g are the means of all beta in period t+1 and t, respec- tively, b- is the slope coefficient of 6 . regressed on 3 , S„,^ and S„^ are the sample variance of 6^., and 6^, respectively. R.,, ^^ is Pt t+X t PT'J.jPt A A the coefficient of determination for regression of 6 . ^ or 6 . Note that Klemkosky and Martin [1975] have used this kind of technique to analyze the performance of alternative beta forcasting technique. To estimate the MSE as indicated in equation (17), data from January, 1965 to March, 1975 are used to estimate the related informa- tion of period t and the data from April, 1975 - September, 1979 are used to estimate the related information in period t+1. The results associated with equation (17) are listed in Table 1. It is found that the MSE of forcasting obtained from the time-varying coefficient beta estimates is smaller than that obtained from constant coefficient beta estimates. The reduction of MSE is essentially due to the reduction of -11- Table 1 MSE of Constant Coefficient Betas and Time-Varying Betas ^t+1 Bt 8t+l et+1, et bias In efficiency random error MSE Constant Coefficient 1.01325 .94682 .30780 .1355 .2396 .03030 .00441 .00880 .05570 .06892 Time-Varying Coefficient .99928 .96648 .42850 .18913 .2448 .10957 .00108 .01168 .05338 .06613 -12- bias. Note that the inefficiency from time-varying coefficient estimate is larger than that for constant coefficient estimates. In sum, it seems reasonable to conclude that the main contribution of time-varying beta estimates in forcasting betas is to reduce the bias. Besides this kind of advantages, the time-varying coefficient can also be used to im^ prove the risk-return trade-off test as shown in the latter portion of this section. Finally, the findings of this paper have other Implications for previous research. Following equation (3), the total risk of each in- dividual security can be decomposed as : (18) VarCY^) = [CF^ + ah^ + 2"Ba, t)Var (X^) ] + [aV + o^]. t 1 1 t n t e 2 If the estimates for both a. and o approach zero, equation (17) can be reduced to: (19) Var(Y^) = J^ Var(X^) + a^. t t e Equation (18) indicates that total risk can be decomposed into system- atic and unsystematic risk by the OLS regression method as discussed by Francis [1979] and others. However, this result does not hold unless g is a deterministic variable. As the beta coefficient is stochastic, the OLS estimate of nonsystematic risk actually has two components, i.e., 2 2 cr X + c . Therefore, the partition of systematic risk and unsystematic risk is not possible since the random risk is confounded with "noise" Fabozzi and Francis (1978) have similar arguments. However, their decomposition is only a special case of our decomposition as In- dicated in equation (18). -13- from shifting betas. Both Lintner [1956] and Douglas [1969] found that the rates of return on individual stocks are strongly correlated with random risk and this is contrary to the capital asset pricing theory. Subse- quently, Miller and Scholes [197] carefully reexamined this issue and still failed to provide a satisfactory explanation. This issue is reexamined in the present study by running two tests. First, the OLS residual variance is used as a measure of random risk, and a simple linear regression is run with the monthly rates of return for each firm as the dependent variable. The results are consistent with Lintner and Douglas's finding that rates of return are strongly correlated with random risk. However, if the "pure residual" variance 2 o is utilized in place of the OLS residual variance, it is found that the relationship between rates of return and random risk is not statis- tically significant. This finding could imply that both Lintner and Douglas's result may be due to the problem of using the fixed beta coef- ficient to decompose the total risk while, in fact, beta is not a con- stant. V. Summary and Concluding Remarks This paper has pointed out some of the problems of previous re- search in the investigation of beta stability and beta tendency. None of the previous studies explicitly derived a model that allows for co- existence of both beta instability and beta tendency. With the applica- tion of the variable mean response regression model, beta can be decom- posed into constant, trend, and random components. The model developed in this study can therefore be considered as a general case of the -14- previous studies. Monthly data for 363 firms was used in this paper to test beta stability and beta tendency. The empirical results revealed that sixty-five percent of the sample firms had significant a values, which indicates that more than half of the firms had an unstable beta over the ten year period. In addition, 105 firms (29%) had significant a. values which implies that a significant portion of the sample firms had shifting betas. The sign and magnitude of ct. is consistent with Blume's [1975] finding that there exists some regression tendency of beta coefficients over time. The MSE of forecasting obtained from the model developed in this paper is smaller than that obtained from the traditional fixed coeffi- cient beta estimates.' This study also reexamined the Lintner and Douglas "paradox." After the elimination of both trend and random components of beta risk, the residual variance was found not to be correlated with the security return. This suggests that the risk partition method that has been used by previous studies may have a fundamental flaw, i.e., random risk can be confounded with "noise" from random betas. To improve esti- mates of beta risk and/or random risk, the model present in this study is a viable alternative. The causes of beta tendency, however, are still unknox^n and future research in this area is needed. -15- References 1. Belkaoui, A. (1977), "Canadian Evidence of Heteroscedasticity in the Market Model," Journal of Finance . 32, pp. 1320-1324. 2. Black, S. W. (1976), "Rational Response to Shocks in a Dynamic Model of Capital Asset Pricing," American Economic Review , 66, pp. 767-779. 3. Blume, M. E. (1971), "On the Assessment of Risk," Journal of Finance . 26, pp. 1-10. 4. Blume, M. E. (1975), "Beta and Their Regression Tendencies," Journal of Finance , 30, pp. 785-95. 5. Cohen, K, and J. 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