A recent paper by six scholars affiliated with Johns Hopkins University investigates how one can make alpha by tracing the foot traffic into brick and mortar stores and engaging in a pairs trading strategy on that basis. Let's back up. What the heck is pairs trading? It is a strategy available any time two investable assets (A and B) are related to one another in a predictable way. Consider Exxon and Chevron. When broad industry factors are the driving force, one would expect that an increase in the value of Exxon would be an increase in the value of Chevron. Their stocks would move in parallel lines. Sometimes, one or the other will move for an idiosyncratic reason -- say, a scandal about the CEO of one of these companies may make headlines, pressing that stock down. That may not impact the other one, or may even drive it up, as people unhappy with the CEO news but still eager to invest in crude oil sell one and buy the other. A pairs trade is typically a trade on a ...