Unmasked: Writers of Negative Online Reviews

July 25, 2013 -- Who's writing all those nasty online reviews—the ones denouncing everything from defective pants to soggy veal piccata? You'd never guess, say two academics who have researched the question.

It's not a few cranky customers, they say. Nor is it some competitor hiding under a pseudonym or paying surrogates to slam a rival.

No, say Eric Anderson and Duncan Simester—professors of marketing at Northwestern University's Kellogg School of Management and MIT's Sloan School of Management, respectively—writers of negative reviews tend to be the best customers of the business or service being criticized. By "best" they mean the most loyal and most valuable (customers who spend the most money).

Your most loyal customers are your most negative reviewers, they conclude, quoting a French maxim ("Your best friends are your hardest critics") to illustrate their point.

The duo's May 2013 paper, "Deceptive Reviews: The Influential Tail," examines more than 325,000 online reviews (both positive and negative) written by customers of a major apparel retailer that sells its wares via stores, catalogs and a website. (The company is not identified by name, but the authors say it has more than 10 million customers).

Anderson and Simester also apply their methodology to 7,219 book reviews (both positive and negative) on Amazon.com.

In both cases, they explain, data collected by the websites makes it possible to match the review-writers to the purchases they may have made.

Anderson tells ABC News that the duo's study breaks new ground, in the respect that most studies of bad reviews have looked not at the behavior of customers but at the behavior of business people trying to make themselves look good (by posting positive reviews of their own goods) or their competitors look bad (by posting negative reviews of a rival's). "Nobody before us has studied individual reviewers," says Andersen.

When he and Simester told apparel company management that they were being slammed by their best customers, he says, "They were surprised." But that was just extraordinary finding #1.

Finding #2: The writers of the most negative reviews had not bought the product they were deploring. In other words, the indignant "This shirt is so flimsy it might as well be tissue paper!" customer hadn't bought the shirt, let alone tried it on.

Write the authors: "The data reveal that approximately 5 percent of the product reviews are written by customers for whom there is no record they have purchased the item," and further, that these reviews "are significantly more negative on average" than the 95 percent written by reviewers who did buy the product. What possibly could be motivating the non-buyers to write negative reviews?

The authors test a variety of theories—each of which is described at length in the paper—before concluding the reviewers are acting as "self-appointed brand managers."

These reviewers like the company, say the authors, as evidenced by the fact that they continue buying after they have penned their negative review. Often, the product they indict is something new--the first men's fragrance, say, by a women's perfume maker. The professors speculate the reviewers want to tell the company it's taken a wrong turn.

"I could see that," says Sarah Gavin, spokesperson for travel site Expedia, which encourages customer reviews. Expedia, she says, does not capture data that would allow it to prove or disprove that explanation, but it makes sense to her intuitively.

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.