Chapter 6: Return and Risk

Chapter 6: Return and Risk
Learning Goals
Understand the meaning and fundamentals of risk, return, and risk aversion.
Describe procedures for measuring the risk of a single asset.
Discuss the risk measurement for a single asset using the standard deviation
and coefficient of variation.
Understand the risk and return characteristics of a portfolio in terms of
correlation and diversification, and the impact of international assets on a
Review the two types of risk and the derivation and role of beta in measuring
the relevant risk of both an individual security and a portfolio.
Explain the capital asset pricing model (CAPM) and its relationship to the
security market line (SML).
If everyone knew ahead of time how much a stock would sell for some time in
the future, investing would be a simple endeavor.
Unfortunately, it is difficult—if not impossible—to make such predictions with
any degree of certainty.
As a result, investors often use history as a basis for predicting the future.
We will begin this chapter by evaluating the risk and return characteristics of
individual assets, and end by looking at portfolios of assets.
Fundamental Concepts about Return and
In the context of business and finance, risk is defined as the chance of
suffering a financial loss.
Assets (real or financial) which have a greater chance of loss are considered
more risky than those with a lower chance of loss.
Risk may be used interchangeably with the term uncertainty to
refer to the variability of returns associated with a given asset.
Return represents the total gain or loss on an investment.
The most basic way to calculate return is as follows:
For example, compute the holding period return if you purchased a stock for
$100, received a $5 dividend, and sold the stock for $110.
Chapter Example Single Financial Assets
 Historical Return
 Arithmetic average
• The historical average (also called arithmetic average or mean) return is simple to
• The accompanying text outlines how to calculate this and other measures of risk and
• All of these calculations were discussed and taught in your introductory statistics
• This slideshow will demonstrate the calculation of these statistics using Microsoft ®
Historical Return
 Arithmetic Average
Single Financial Assets
 Historical Risk
 Variance
• Historical risk can be measured by the variability of an asset’s returns in relation to its
• Variance is computed by summing squared deviations and dividing by the number of
observations minus one (n - 1).
• Squaring the differences ensures that both positive and negative deviations are given
equal consideration.
• The sum of the squared differences is then divided by the number of observations
minus one (n - 1).
 Historical Risk
 Standard deviation
• Squaring the deviations makes the variance difficult to interpret.
• In other words, by squaring percentages, the resulting deviations are in percent
squared terms.
• The standard deviation simplifies interpretation by taking the square root of the squared
• In other words, standard deviation is in the same units as the computed average.
• If the average is 10%, the standard deviation might be 20%, whereas the variance
would be 20% squared.
 Expected Return and Risk
 Investors and analysts often look at historical returns as a starting point for
predicting the future.
 However, they are much more interested in what the returns on their
investments will be in the future.
 For this reason, we need a method for estimating future or “ex-ante”
 One way of doing this is to assign probabilities for future states of nature
and the returns that would be realized if a particular state of nature does
 Coefficient of Variation (CV)
 One problem with using standard deviation as a measure of risk is that we
cannot easily make risk comparisons between two assets.
 The coefficient of variation overcomes this problem by measuring the
amount of risk per unit of return.
 The higher the coefficient of variation, the more risk per return.
 Therefore, if given a choice, an investor would select the asset with the
lower coefficient of variation.
Portfolio of Assets
 An investment portfolio is any collection or combination of financial assets.
 If we assume all investors are rational and therefore risk averse, that investor will ALWAYS
choose to invest in portfolios rather than in single assets.
 Investors will hold portfolios because he or she will diversify away a portion of the risk that is
inherent in “putting all your eggs in one basket.”
 If an investor holds a single asset, he or she will fully suffer the consequences of poor
 This is not the case for an investor who owns a diversified portfolio of assets.
 Diversification is enhanced depending upon the extent to which the returns on assets “move”
 This movement is typically measured by a statistic known as correlation as shown in Figure
6.3 below.
 Even if two assets are not perfectly negatively correlated, an investor can still realize
diversification benefits from combining them in a portfolio as shown in Figure 6.4 below.
Capital Asset Pricing Model (CAPM)
 If you notice in the last slide, a good part of a portfolio’s risk (the standard deviation of
returns) can be eliminated simply by holding a lot of stocks.
 The risk you can’t get rid of by adding stocks (systematic) cannot be eliminated through
diversification because that variability is caused by events that affect most stocks similarly.
 Examples would include changes in macroeconomic factors such interest rates, inflation,
and the business cycle.
Capital Asset Pricing Model (CAPM)
 In the early 1960s, researchers (Sharpe, Treynor, and Lintner) developed an asset pricing
model that measures only the amount of systematic risk a particular asset has.
 In other words, they noticed that most stocks go down when interest rates go up, but some
go down a whole lot more.
 They reasoned that if they could measure this variability—the systematic risk—then they
could develop a model to price assets using only this risk.
 The unsystematic (company-related) risk is irrelevant because it could easily be eliminated
simply by diversifying.
Capital Asset Pricing Model (CAPM)
 To measure the amount of systematic risk an asset has, they simply regressed the returns
for the “market portfolio”—the portfolio of ALL assets—against the returns for an individual
 The slope of the regression line—beta—measures an asset’s systematic (nondiversifiable) risk.
 In general, cyclical companies like auto companies have high betas while relatively stable
companies, like public utilities, have low betas.
 Let’s look at an example to see how this works.
 Capital Asset Pricing Model (CAPM)
 The required return for all assets is composed of two parts: the risk-free
rate and a risk premium.
 The risk premium is a function of both market conditions and the asset
 The risk-free rate (rf) is usually estimated from the return on U.S. T-Bills.
 The risk premium for a stock is composed of two parts:
• The market risk premium, which is the return required for investing in any risky asset
rather than the risk-free rate.
• Beta, a risk coefficient which measures the sensitivity of the particular stock’s return to
changes in market conditions.
 After estimating beta, which measures a specific asset’s systematic risk, relatively easy to
estimate variables may be obtained to calculate an asset’s required return.
 Example
• Calculate the required return for Federal Express assuming it has a beta of 1.25, the
rate on U.S. T-Bills is 5.07%, and the expected return for the S&P 500 is 15%.
 Some Comments on the CAPM
 The CAPM is based on an assumed efficient market with the following
• Many small investors each having the same information and expectations with respect
to securities
• Rational investors who are risk averse
• No restrictions on investment
• No taxes
• No transactions costs
 Because these assumptions do not strictly hold, the CAPM should only be
viewed as a useful conceptual framework for understanding the risk and
return on an investment.
 In addition, the data used to approximate the beta and other components of
the CAPM are historical.
 Because the CAPM is an expectational model, these variables may or may
not reflect the future variability of returns.
Related documents