A decade or so after they entered supermarkets, opinions remain divided about self-service checkout lanes. My Type A assistant thinks they are the orange cat’s pajamas. My other assistant, a world-class slug, prefers that clerks handle their traditional duties, no matter how untrained. (“This isn’t scanning. Do you remember how much the sign said it was?”)

Grocery chains figured the technology would catch on quickly and produce savings in personnel costs. But now there is evidence that using the honor system at checkout has produced a new breed of criminal: the otherwise law-abiding shoplifter. The New York Times reports on research done by two college professors in England:

“The study examined nearly 12 million shopping trips from four retailers in Britain, two in the United States and one each in Belgium and the Netherlands from December 2013 to February 2015. One million shopping trips were audited in detail, amounting to 6 million items checked. Nearly 850,000 were found not to have been scanned, the report said, making up nearly 4% of the total value of the purchases.”

Given the small margins in the grocery business, that’s a lot of shrinkage. Seeing that one bored employee giving six time-strapped shoppers the evil eye may not be working all that well, some retailers have installed Big Brother cameras. But they can’t be monitored in real time, and hiding an overpriced greeting card behind three gallons of laundry detergent hardly requires the dexterity of Penn & Teller.

There will always be accidents and thieves, but the area that seems to most alarm retailers is customers who rationalize that they are entitled to a few freebies now and then. From The Times:

“In a behavior known as ‘neutralizing your guilt,’ shoppers may tell themselves that the store is overpriced, so taking an item without scanning is acceptable, or they might blame faulty technology or problems with product bar codes, or claim a lack of technical know-how, the report said. The study quoted one respondent as saying that people who do not normally steal may come to realize that ‘when I buy 20, I can get five for free.’ ”