Why, though, would reviewers feel a need to lie about having bought the product? Why wouldn't they just say, "I didn't buy this French beret, and I never would. I'm ashamed to see it being sold by L.L.Bean. I come here for the good old Maine Hunting Shoe, not for French accessories."
"I think they are looking for credibility," surmises Simester. "It's not so surprising they would try to give their review greater weight by claiming they had bought the item."
How widespread and how pernicious does he think this problem is: loyal customers slamming products they have never bought? "I think that, if anything, we underestimate the importance of this effect," he tells ABC News. Research shows, he says, that negative reviews have a harmful effect on sales.
He and Anderson think their research may prompt more businesses to make the purchase of an item a precondition for its being reviewed. That's the way Expedia, for example, operates. Says Gavin: "Once we know you've booked your hotel room, that you've paid and checked out, you can write your review. Otherwise, you cannot access that portal."
She says Expedia is set up that way precisely to prevent the kind of deception documented by the professors: People pretending to review a product or service they haven't tried.