Self-checkout theft has become so widespread that a whole lingo has sprung up to describe its tactics. Ringing up a T-bone ($13.99/lb) with a code for a cheap ($0.49/lb) variety of produce is “the banana trick.” If a can of Illy espresso leaves the conveyor belt without being scanned, that’s called “the pass around.” “The switcheroo” is more labor-intensive: Peel the sticker off something inexpensive and place it over the bar code of something pricey. Just make sure both items are about the same weight, to avoid triggering that pesky “unexpected item” alert in the bagging area.

How common are self-scanning scams? If anonymous online questionnaires are any indication, very common. When Voucher Codes Pro, a company that offers coupons to internet shoppers, surveyed 2,634 people, nearly 20 percent admitted to having stolen at the self-checkout in the past. More than half of those people said they gamed the system because detection by store security was unlikely. A 2015 study of self-checkouts with handheld scanners, conducted by criminologists at the University of Leicester, also found evidence of widespread theft. After auditing 1 million self-checkout transactions over the course of a year, totaling $21 million in sales, they found that nearly $850,000 worth of goods left the store without being scanned and paid for.