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You Can't Become Rich In Your Pocket Until You Become Rich In Your Mind | ||||
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On investments with equity risk, the risk is best measured by looking at the variance of actual returnsSummary Risk, as we define it in finance, is measured based upon deviations of actual returns on an investment from its expected returns. There are two types of risk. The first, which we call equity risk, arises in investments where there are no promised cash flows, but there are expected cash flows. The second, default risk, arises on investments with promised cash flows. On investments with equity risk, the risk is best measured by looking at the variance of actual returns around the expected returns, with greater variance indicating greater risk. This risk can be broken down into risk that affects one or a few investments, which we call firm specific risk, and risk that affects many investments, which we refer to as market risk. When investors diversify, they can reduce their exposure to firm specific risk. By assuming that the investors who trade at the margin are well diversified, we conclude that the risk we should be looking at with equity investments is the market risk. The different models of equity risk introduced in this chapter share this objective of measuring market risk, but they differ in the way they do it. In the capital asset pricing model, exposure to market risk is measured by a market beta, which estimates how much risk an individual investment will add to a portfolio that includes all traded assets. The arbitrage pricing model and the multi-factor model allow for multiple sources of market risk and estimate betas for an investment relative to each source. Regression or proxy models for risk look for firm characteristics, such as size, that have been correlated with high returns in the past and use these to measure market risk. In all these models, the risk measures are used to estimate the expected return on an equity investment. This expected return can be considered the cost of equity for a company. On investments with default risk, risk is measured by the likelihood that the promised cash flows might not be delivered. Investments with higher default risk should have higher interest rates and the premium that we demand over a riskless rate is the default premium. For most US companies, default risk is measured by rating agencies in the form of a company rating; these ratings determine, in large part, the interest rates at which these firms can borrow. Even in the absence of ratings, interest rates will include a default premium that reflects the lenders assessments of default risk. These default-risk adjusted interest rates represent the cost of borrowing or debt for a business Problems 1. The following table lists the stock prices for Microsoft from 1989 to 1998. The company did not pay any dividends during the period a. Estimate the average annual return you would have made on your investment. b. Estimate the standard deviation and variance in the annual returns. c. If you were investing in Microsoft today, would you expect the historical standard deviations and variances to continue to hold? Why or why not? 2. Unicom is a regulated utility serving Northern Illinois. The following table lists the stock prices and dividends on Unicom from 1989 to 1998. a. Estimate the average annual return you would have made on your investment. b. Estimate the standard deviation and variance in the annual returns. c. If you were investing in Unicom today, would you expect the historical standard deviations and variances to continue to hold? Why or why not? 3. The following table summarizes the annual returns you would have made on two companies Scientific Atlanta, a satellite and data equipment manufacturer, and AT&T, the telecomm giant, a. Estimate the average and standard deviation in annual returns in each company. b. Estimate the covariance and correlation in returns between the two companies. c. Estimate the variance of a portfolio composed, in equal parts, of the two investments. 4. You are in a world where there are only two assets, gold and stocks. You are interested in investing your money in one, the other or both assets. Consequently you collect the following data on the returns on the two assets over the last six years. a. If you were constrained to pick just one, which one would you choose? b. A friend argues that this is wrong. He says that you are ignoring the big payoffs that you can get on gold. How would you go about alleviating his concern? c. How would a portfolio composed of equal proportions in gold and stocks do in terms of mean and variance? d. You now learn that GPEC (a cartel of gold-producing countries) is going to vary the amount of gold it produces with stock prices in the US. (GPEC will produce less gold when stock markets are up and more when it is down.) What effect will this have on your portfolios? Explain. 5. You are interested in creating a portfolio of two stocks - Coca Cola and Texas Utilities. Over the last decade, an investment in Coca Cola stock would have earned an average annual return of 25% with a standard deviation in returns of 36%. An investment in Texas Utilities stock would have earned an average annual return of 12%, with a standard deviation of 22%. The correlation in returns across the two stocks is 0.28. a. Assuming that the average and standard deviation, estimated using past returns, will continue to hold in the future, estimate the average returns and standard deviation of a portfolio composed 60% of Coca Cola and 40% of Texas Utilities stock. b. Estimate the minimum variance portfolio. c. Now assume that Coca Colas international diversification will reduce the correlation to 0.20, while increasing Coca Colas standard deviation in returns to 45%. Assuming all of the other numbers remain unchanged, answer (a) and (b). 6. Assume that you have half your money invested in Times Mirror, the media company, and the other half invested in Unilever, the consumer product giant. The expected returns and standard deviations on the two investments are summarized below: Estimate the variance of the portfolio as a function of the correlation coefficient (Start with -1 and increase the correlation to +1 in 0.2 increments). 7. You have been asked to analyze the standard deviation of a portfolio composed of the following three assets: Estimate the variance of a portfolio equally weighted across all three assets. 9. Assume that the average variance of return for an individual security is 50 and that the average covariance is 10. What is the expected variance of a portfolio of 5, 10, 20, 50 and 100 securities. How many securities need to be held before the risk of a portfolio is only 10% more than the minimum? 10. Assume you have all your wealth (a million dollars) invested in the Vanguard 500 index fund and that you expect to earn an annual return of 12% with a standard deviation in returns of 25%. Since you have become more risk averse, you decide to shift $200,000 from the Vanguard 500 index fund to treasury bills. The T.bill rate is 5%. Estimate the expected return and standard deviation of your new portfolio. 11. Every investor in the capital asset pricing model owns a combination of the market portfolio and a riskless asset. Assume that the standard deviation of the market portfolio is 30% and that the expected return on the portfolio is 15%. What proportion of the following investors wealth would you suggest investing in the market portfolio and what proportion in the riskless asset? (The riskless asset has an expected return of 5%) a. an investor who desires a portfolio with no standard deviation b. an investor who desires a portfolio with a standard deviation of 15% c. an investor who desires a portfolio with a standard deviation of 30% d. an investor who desires a portfolio with a standard deviation of 45% e. an investor who desires a portfolio with an expected return of 12% 12. The following table lists returns on the market portfolio and on Scientific Atlanta, each year from 1989 to 1998. Year Scientific Atlanta Market Portfolio a. Estimate the covariance in returns between Scientific Atlanta and the market portfolio. b. Estimate the variances in returns on both investments. c. Estimate the beta for Scientific Atlanta. 13. United Airlines has a beta of 1.50. The standard deviation in the market portfolio is 22% and United Airlines has a standard deviation of 66% a. Estimate the correlation between United Airlines and the market portfolio. b. What proportion of United Airlines risk is market risk? 14. You are using the arbitrage pricing model to estimate the expected return on Bethlehem Steel, and have derived the following estimates for the factor betas and risk premia: a. Which risk factor is Bethlehem Steel most exposed to? Is there any way, within the arbitrage pricing model, to identify the risk factor? b. If the riskfree rate is 5%, estimate the expected return on Bethlehem Steel. c. Now assume that the beta in the capital asset pricing model for Bethlehem Steel is 1.1 and that the risk premium for the market portfolio is 5%. Estimate the expected return using the CAPM. d. Why are the expected returns different between the two models? 15. You are using the multi-factor model to estimate the expected return on Emerson Electric, and have derived the following estimates for the factor betas and risk premia: where MV is the market value of equity in hundreds of millions of dollar and BV is the book value of equity in hundreds of millions of dollars. The return is a monthly return. a. Estimate the expected annual return on Lucent Technologies. The market value of equity is $240 billion and the book value of equity is $13.5 billion. b. Lucent Technologies has a beta of 1.55. If the riskless rate is 6%, and the risk premium for the market portfolio is 5.5%, estimate the expected return. c. Why are the expected returns different under the two approaches? |
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