Which is faster — an express line with multiple shoppers or a regular line with one shopper who has a large basket?
That question has obsessed California math teacher Dan Meyer for years. “It's my Da Vinci Code,” he says on his blog (http://blog.mrmeyer.com/?p=4646).
What complicates the problem is that “there are easily a dozen variables affecting the line speed that have nothing to do with the number of customers in each line or the number of items in their baskets,” he writes.
Still, six hours' worth of checkout data provided by a store manager shed some light on the problem. His conclusion: The express lane isn't faster. “When you add one person to the line, you're adding 48 extra seconds to the line length (tender time plus “other” time) without even considering the items in her cart. Meanwhile, an extra item only costs you an extra 2.8 seconds. Therefore you'd rather add 17 more items to the line than one extra person!
“I can't believe I'm dropping exclamation points in an essay on grocery shopping but that's how this stuff makes me feel.”