A Matter of Perception

May 17th 2007
From The Economist print edition
Averages need to be treated with caution

CONSIDER these two statements: the American stockmarket was overvalued in 2000; company profits are high relative to economic output. Many people would agree with both propositions, but implicit in each is that there is a correct, or normal, value for shares or profits. The corollary is that when share price or profits are too high or too low, they will eventually revert to the mean. But what do people mean by mean? Efficient-market theory, which states that prices already reflect all available information, presents an immediate problem for the idea of a reversion to the mean. If share prices were obviously too high, investors would sell their holdings until prices fell to the correct level. There would be no extremes to revert from. However, in the light of the dotcom bubble, it seems inherently unsatisfying to argue that markets are always fairly valued. Such a position also gives a green light to those who argue that “it's different this time”, and who use any old valuation measure (price per eyeball for internet stocks) to justify share prices. Pinning down the right mean, however, is difficult. American profits look high by the standards of the past 20 to 30 years. But they do not look unreasonable relative to 1950s and 1960s levels. Perhaps the 1970s and 1980s (which saw high inflation and double-digit interest rates) were the aberration and the immediate post-war era was the norm. Things get even more complicated when investors start to talk about stockmarket valuations. Most analysts tend to use the prospective price-earnings ratio as their chosen measure, rather than the historic figure. They justify this by saying that investors look forward, not back. But banks are in the business of selling shares. Since analysts nearly always forecast rising profits, the prospective p/e ratio is usually lower than the historic one; that makes the market sound cheaper.

Finding "cheaper" is not the objective. Buying and selling to a profit is the objective.

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