Here’s a different sort of grocery store math than you’re probably used to. A high school math teacher in Santa Cruz, California drew up a lesson plan for teaching students to answer the question: “which checkout line is the fastest?” Clearly, this is education after our own hearts. You may have your own anecdata on this subject, and even try to make predictions as you choose your line and thus your destiny, but that is no match for science.
The conclusions, after studying the lines in his local store as well as cash register data: it’s people that slow down the checkout process, not items, and the express line is slower when all other things are equal.
The express lane isn’t faster. The manager backed me up on this one. You attract more people holding fewer total items, but as the data shows above, when you add one person to the line, you’re adding 48 extra seconds to the line length (that’s “tender time” added to “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.
We know the feeling!