The Economist reported on the strong correlation between the United States’ obesity rate and the distance that an average driver drives. They suggested (with caveats) that the increase in the amount that Americans drive might be causing high obesity rates. Justin Wolfers at Freakonomcis was unsatisfied with this argument and noted that his age was a better explanatory variable for the rise in obesity rates. He went on to argue that the correlation between miles driven and rates of obesity was incidental.
We should get a better sense of whose right in 2014 when America’s obesity rate is predicted to decline (due to a decrease in average miles driven), despite a (predicted) increase in Wolfer’s age.