The Effect of Word of Mouth on Sales: Online Book Reviews

The authors examine the effect of consumer reviews on relative sales of books at Amazon.com and Barnesandnoble.com . The authors find that (1) reviews are overwhelmingly positive at both sites, but there are more reviews and longer reviews at Amazon.com ; (2) an improvement in a book's reviews leads to an increase in relative sales at that site; (3) for most samples in the study, the impact of one-star reviews is greater than the impact of five-star reviews; and (4) evidence from review-length data suggests that customers read review text rather than relying only on summary statistics.