In 1980, the econometrician David Hendry (now Sir David) investigated a key economic question: what causes inflation? Hendry looked to the data for insight. He speculated that a particular variable, X, was largely responsible. He assembled data on variable X, performed a few deft mathematical tweaks and compared his transformed X with the path of consumer prices in the UK. Graphing the result showed an astonishingly close fit.
The only snag: X was cumulative rainfall. Since consumer prices and cumulative rainfall both rise over time, Hendry had an excellent platform for finding his spurious correlation. Statistical sleight of hand did the rest.
Hendry wanted to demonstrate just how easy it was to produce plausible nonsense by misusing the tools of statistics. “It is meaningless to talk about ‘confirming’ theories when spurious results are so easily obtained,” he wrote.