“The Effect of Word of Mouth on Sales: Online Book Reviews”, synthesis.

J. Chevalier and D. Mayzlin in their paper wanted to show us the reviewer behaviour in the two main online booksellers’ sites: BarnesandNoble.com and Amazon.com, and they examined the effect of consumer reviews on firms’ sales. In that aim they saw the influence of the online user reviews on consumers like word of mouth about the quality of books. Quickly it appears different problems.
Why do consumers need to leave reviews? Do they have to buy books where they find good reviews on? Consumers can leave wrong reviews on a site as authors and publishers can leave favourable reviews on their sites which make a bias in the results.
In their works they tried to determinate the direction of causality between word of mouth and product sales by comparing the sales of a given book across the two booksellers. But in order to be common to both booksellers, they examined the relationship between market shares and customer reviews for a given book across the two sites. It appears that the two sites are very similar in terms of customer preferences and reviewer behaviour and they examine the positive and negative reviews on sales.
In the following parts, they described the data and the methodology before to present results on the distribution of reviews and sales across sites and the empirical analysis of the effect of “word of mouth” reviews on product sales.

By Frédéric Héas, Benoît Bourné and Maxime Le Clerc de la Herverie.

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