
Relationships between investments:
portfolio theory
9
Learning objectives
This chapter is designed to explore the financial equivalent of the maxim ‘don’t put all your eggs in
one basket’. In particular, it aims:
■ To give the reader an understanding of the rationale behind the diversification decisions of both
shareholders and companies.
■ To illustrate the mechanics of portfolio construction with a user-friendly approach to statistics,
using numerical examples.
■ To explain why optimal portfolio selection is a matter of personal choice.
■ To examine the drawbacks of portfolio analysis as an approach to project appraisal.
A good grasp of the principles of portfolio analysis is an essential underpinning to understanding the
Capital Asset Pricing Model, to be covered in Chapter 10.
LEX LIVE
Metro and the weather
FT
Diversified investment strate-
gies can be marvellous things.
Suppose you face a choice of
buying shares in a maker of
sunscreen or in a maker of
umbrellas. The textbook
response is to invest in both.
This guarantees a relatively
high return at moderate risk
levels, whatever the weather.
The same logic should apply
to companies, too. Unfortuna-
tely, that has not been the
recent experience of investors.
On Friday, Metro, the German
retail conglomerate, joined the
growing list of companies
blaming their lacklustre per-
formance on a rainy European
summer.
Wet weather may indeed
have hit Metro’s food sales.
But the argument would carry
more weight had the very
same Metro a year ago not put
weak department store sales
down to last summer’s heat.
Groups such as Unilever and
Cadbury Schweppes have also
been keen to use the weather
excuse in recent years, freely
invoking the vagaries of the
climate to explain away their
performance.
This might sound like harm-
less spin, but it contains a real
danger. This is that companies
may actually believe their own
PR and start to overlook struc-
tural challenges, such as the
growth of own labels and dis-
count retailers. These affect
both Unilever and – arguably –
Metro. The German retailer’s
weak like-for-like sales growth
partly reflects lacklustre
demand. But it also raises
some doubts about the returns
of its foreign expansion. When
companies diversify, they take
on a huge extra burden of
management. If Metro cannot
even cope with whatever is
thrown at it by the weather
gods, it should reconsider its
foray abroad – and leave the
task of diversifying to
investors.
Source: Financial Times, 29 October 2004.
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