Intuition, Math & The Supermarket Checkout

The Wall Street Journal: “We are used to the standard system of one line for each cashier. But what if there is just one big lane feeding multiple cashiers? … The single queue often snakes around, as lines do at airport security checkpoints. Mathematical queuing theory says that the serpentine system should be faster than separate lines leading to separate cash registers, but only with a condition called ‘no jockeying’—the assumption that people in multiple lines won’t hop over to a different line that has become free.”

“But that isn’t realistic, as we can all attest. If you allow jockeying in multiple lines, the serpentine system is no faster on average. It might intuitively seem faster because you won’t get stuck behind a single person taking a long time, but that same delay is just portioned out among more people, leaving the average wait time the same … In a curious twist, one recent study showed that cashiers work faster when they are serving a dedicated line. Perhaps it instills a sense of pride or connection with the customers waiting for one hardworking cashier.”

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