Although he conceded there are "easily a dozen" variables involved, Meyer determined that adding one person to a queue adds a minimum of 48 seconds to the checkout speed, not even counting the number of items each person is buying. "Meanwhile, an extra item only costs you an extra 2.8 seconds," Meyer wrote. "Therefore, you'd rather add 17 more items to the line than one extra person!" That means the Express Lane is often the wrong choice. However, as we all know, it takes just six words from a cashier to derail the best calculation: "I need a price check, please."
It is one of modern mankind's most profound questions: Which checkout line at the supermarket is the best choice? Will choosing the Express Lane, with its four shoppers carrying a couple of items each, get you out of there faster than the regular lane with one shopper and her cartful of groceries? On his blog, California math teacher Dan Meyer said he's been "obsessed" for years over finding a mathematical way to choose the fastest checkout line. "It's my DaVinci code," wrote Meyer. So he spent hours watching grocery store queues, reviewing POS data and making calculations.