The Effect Of Word Of Mouth On Sales: Online Book Reviews (Research Seminar, April 21st, 2004) Judith Chevalier Yale University Abstract We examine the effect of consumer reviews on relative sales of books on Amazon.com and BarnesandNoble.com. We 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, and 3) the impact of 1-star reviews is greater than the impact of 5-star reviews.