Do Reviews on Amazon Matter?

One study suggests they do—especially very negative ones.
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One study suggests they do—especially very negative ones.
(Photo: Twin Design/Shutterstock)

(Photo: Twin Design/Shutterstock)

Do positive reviews on really make a difference? It appears they do—although not as much as really negative reviews.

That finding, laid out in a 2006 research paper, is of renewed interest given the news that the giant Internet retailer has sued three websites it accuses of selling, and posting, fake positive reviews.

According to a Seattle Times report, the suit accused the sites of charging $19 to $22 per review for the service, and alleges they “deceive consumers and harm the sellers on Amazon’s site who don’t game the system.”

In the August 2006 edition of the Journal of Marketing Research, Yale University researchers Judith Chevalier and Dina Mayzlin examined the actual effect of book reviews on both and They looked at the star ratings received by 1,087 books that were offered for sale during three two-day periods in 2003 and 2004, and which had reviews posted at both sites.

"The relatively rare one-star reviews carry a lot of weight with consumers.”

“An increase in the average star rating on over time results in higher relative sales of the book on over time (one month after the reviews under consideration have been posted),” they write.

That said, “we find evidence that one-star reviews have a greater impact than five-star reviews on the same site," Chevalier and Mayzlin add.

"The relatively rare one-star reviews carry a lot of weight with consumers,” the researchers write. “This results makes sense when the credibility of one-star and five-star reviews are considered. After all, the author, or another interested party, may ‘hype’ his or her own book by publishing glowing reviews on those websites.”

Their results suggest that, to some extent, customers realize this and take five-star reviews with a grain of salt. One-star reviews, however, get their attention.

Another interesting point the researchers make: While “it seems plausible to speculate that the total number of books sold at is higher than it would be without the provision of customer review features,” the evidence “stops short of showing that retailers profit from providing such content.”

It’s entirely possible, they write, that reviews simply “move sales around across books within a site.” If a book you’re looking at receives bad reviews, you might just keep searching until you find an interesting-sounding one that received good notices. Either way, Amazon gets a sale.

Still, any business wants to retain its long-term credibility, and if customers are already wary of five-star reviews, it makes sense that Amazon would want to put an end to what it sees as the blatant practice of buying and selling them.