
238 Part III Investment risk and return
10.1 INTRODUCTION
In Chapters 8 and 9, we examined various methods of handling risk and uncertainty in
project appraisal, ranging from sensitivity analysis to diversification to exploit the less
than perfect correlation between the returns from risky investments. Most of these
approaches aim to identify the sources and extent of project risk and to assess whether
the expected returns sufficiently compensate investors for bearing the risk. Utility the-
ory suggests that, as risk increases, rational risk-averse people require higher returns,
justifying the common practice of adjusting discount rates for risk. However, none of
these approaches offers an explicit guide to measuring the precise reward investors
should seek for incurring a particular level of risk.
The CAPM is a theory originally devised by Sharpe (1964) to explain how the cap-
ital market sets share prices. It now provides the infrastructure of much of modern
financial theory and research and offers important insights into measuring risk and
setting risk premiums. In particular, it shows how the study of security prices can help
in assessing required rates of return on investment projects. However, as we shall see,
the CAPM has not gone unchallenged.
10.2 SECURITY VALUATION AND DISCOUNT RATES
Asset value is governed by two factors – the stream of expected benefits from holding
the asset and their ‘quality’, or likely variability. For example, the value of a single-
project company is assessed by discounting future project cash flows at a discount rate
reflecting their risk. The value, of a company newly formed by issuing one million
shares to exploit a one-year project offering a single net cash flow of at a
25 per cent discount rate, is:
This suggests a market price per share of This would be the
value established by an efficient capital market taking account of all known informa-
tion about the company’s future prospects.
Sometimes, the ‘correct’ discount rate is unclear to the firm. A major contribution of
the CAPM is to explain how discount rates are established and hence how securities
are valued. However, from the capital market value of a company, we can ‘work back-
wards’ to infer what discount rate underlies the market price. In the example, if we
observe a market price of this suggests a required return of 25 per cent.
By implication, if the market sets a value on a security that implies a particular dis-
count rate, it is reasonable to conclude that any further activity of similar risk to current
operations should offer at least the same rate. This argument depends critically on
market prices being unbiased indicators of the intrinsic worth of companies, i.e. that
the Efficient Markets Hypothesis applies.
Any discount rate is an amalgam of three components:
1 Allowance for the time value of money – the compensation required by investors
for having to wait for their payments.
2 Allowance for price level changes – the additional return required to compensate
for the impact of inflation on the real value of capital.
3 Allowance for risk – the promised reward that provides the incentive for investors
to expose their capital to risk.
Ignoring expected inflation (or assuming that it is ‘correctly’ built into the structure
of interest rates), discount rates have two components – the rate of return required on
totally risk-free assets, such as government securities, and a risk premium.
£8
1£8 m>1 m shares2 £8.
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o
£10 m
11.252
£8 m
£10 million,
V
o
,
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