Friday, August 03, 2007

Mark Sellers: Tend to overanalyse stocks? Bring out the dart-wielding monkey

Should you spend countless hours researching a stock before buying it, or just a few hours? The common wisdom is that the more time you spend on research, the better your investment results will be. But is this correct?

Not according to studies on the subject. At least two I have seen came to the conclusion that anything more than a cursory review of a company’s prospects is a waste of time. One study looked at whether more information was useful to experienced horse racing gamblers. The researchers first gave the gamblers a few items of relevant information (age of horse, pedigree, jockey, etc) and asked them to predict which horse would win the race.

They then gave out dozens more items of information about the race and asked the experts to predict again, based on the additional information they had received. The conclusion was that the first few items of information given to them were useful but further information had no effect on the accuracy of their predictions. The gamblers were far more confident about their predictions after receiving more information, but this didn’t translate into accuracy.

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