Politicas

Signifying nothing?
Jan 29th 2004 From The Economist print edition Too many economists misuse statistics FIGURES lie, as everyone knows, and liars figure. That should make economists especiallysuspect, since they rely heavily on statistics to try and resolve a wide range of controversies. For example, does a rise in the minimum wage put people out of work? Are stockmarket returns predictable?Do taxes influence whether a company pays dividends? In recent years, helped by cheaper, more powerful computers, and egged on by policy-makers anxious for their views, economists have analysed reamsof statistics to answer such questions. Unfortunately, their guidance may be deeply flawed. Two economists, Deirdre McCloskey of the University of Illinois, and Stephen Ziliak of Roosevelt University,think their colleagues do a lousy job of making sense of figures, often falling prey to elementary errors. But their biggest gripe is that, blinded by statistical wizardry, many economists fail tothink about the way in which the world really works. To be fair, statistics can be deceptive, especially when explaining human behaviour, which is necessarily complicated, and to which iron laws do notapply. Moreover, even if a relationship exists, the wrong conclusions can be drawn. In medieval Holland, it was noted that there was a correlation between the number of storks living on the roof of ahouse and the number of children born within it. The relationship was so striking that, according to the rules of maths that govern such things, you could say with great confidence that the resultswere very unlikely to be merely random. Such a relationship is said to be “statistically significant”. But the Dutch folklore of the time that storks somehow increased human fertility was clearly wrong.Examples of similar errors abound. W.S. Jevons, an English economist of the mid-19th century, thought that sunspots influenced crop yields. More recently and tragically, British mothers have felt...