Shopping mall foot traffic

It is a truth universally acknowledged that when Americans decide to buy more things in shopping malls, postal carriers across the nation are simultaneously bitten by dogs with the enthusiasm of a coordinated military campaign. One might expect consumer spending to correlate with, say, retail employment or credit card debt—things that live in the same conceptual neighbourhood. Instead we have discovered that the desire to purchase a cinnamon pretzel in February moves in perfect 92-percent lockstep with the likelihood that a mail carrier in Nebraska will have their calf examined by a German Shepherd's teeth. The universe, it turns out, is not above cosmic pranks.

The actual mechanism here is almost certainly neither mysterious nor nefarious, which is disappointing in its own way. Both mall foot traffic and dog bite incidents track reliably against population growth and seasonal weather patterns—more people moving around in spring and summer means more shoppers wandering toward the food court and more mail carriers walking neighbourhoods when it is warm enough to be outside without regret. Add in economic cycles (good times bring mall visits; population density brings more dogs) and you have a situation where two completely unrelated human activities are being herded along by the same invisible hand: American seasons and American appetite. Over seven years, that hand barely wavered, which is almost impressive in the way that watching a broom fall always fall bristles-down is almost impressive.

What we are witnessing is not that shopping malls cause dog bites, nor that anxious dogs cause mall traffic, but rather that we live in a world of such interconnected momentum that nearly any two steadily growing datasets will eventually dance together like passengers on the same crowded train. The correlation is real; the causation is imaginary; and we are all of us slightly less intelligent for having learned this. The numbers agree on almost nothing.