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CHAPTER 8. Index Models. Reduces the number of inputs for diversification Easier for security analysts to specialize. Advantages of the Single Index Model. ß i = index of a securities’ particular return to the factor m = Unanticipated movement related to security returns
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CHAPTER 8 Index Models
Reduces the number of inputs for diversification Easier for security analysts to specialize Advantages of the Single Index Model
ßi = index of a securities’ particular return to the factor m = Unanticipated movement related to security returns ei = Assumption: a broad market index like the S&P 500 is the common factor. Single Factor Model
Single-Index Model Regression Equation: Expected return-beta relationship:
Single-Index Model Continued Risk and covariance: Total risk = Systematic risk + Firm-specific risk: Covariance = product of betas x market index risk: Correlation = product of correlations with the market index
Index Model and Diversification Portfolio’s variance: Variance of the equally weighted portfolio of firm-specific components: When n gets large, becomes negligible
Figure 8.1 The Variance of an Equally Weighted Portfolio with Risk Coefficient βp in the Single-Factor Economy
Figure 8.2 Excess Returns on HP and S&P 500 April 2001 – March 2006
Figure 8.3 Scatter Diagram of HP, the S&P 500, and the Security Characteristic Line (SCL) for HP
Table 8.1 Excel Output: Regression Statistics for the SCL of Hewlett-Packard
Alpha and Security Analysis Macroeconomic analysis is used to estimate the risk premium and risk of the market index Statistical analysis is used to estimate the beta coefficients of all securities and their residual variances, σ2 ( e i ) Developed from security analysis
Alpha and Security Analysis Continued The market-driven expected return is conditional on information common to all securities Security-specific expected return forecasts are derived from various security-valuation models The alpha value distills the incremental risk premium attributable to private information Helps determine whether security is a good or bad buy
Single-Index Model Input List Risk premium on the S&P 500 portfolio Estimate of the SD of the S&P 500 portfolio n sets of estimates of Beta coefficient Stock residual variances Alpha values
Optimal Risky Portfolio of the Single-Index Model Maximize the Sharpe ratio Expected return, SD, and Sharpe ratio:
Optimal Risky Portfolio of the Single-Index Model Continued Combination of: Active portfolio denoted by A Market-index portfolio, the (n+1)th asset which we call the passive portfolio and denote by M Modification of active portfolio position: When
The Information Ratio The Sharpe ratio of an optimally constructed risky portfolio will exceed that of the index portfolio (the passive strategy):
Figure 8.5 Efficient Frontiers with the Index Model and Full-Covariance Matrix
Table 8.2 Comparison of Portfolios from the Single-Index and Full-Covariance Models
Table 8.3 Merrill Lynch, Pierce, Fenner & Smith, Inc.: Market Sensitivity Statistics