The latest Physics News Update reports on a recent Physical Review Letters article which reports an analysis of sales ranking data from Amazon (see the sciscoop book search on the left!) Of course the authors aren’t so much interested in books as in generic “complex networks” – and the various “shocks” to such a network that, in the case of books, can propel something to the bestseller lists.
Typical of complex behavior, the authors find power law growth and decay when the causes of change are internal (“endogenous”) to the network – i.e. word-of-mouth transmission of information in the case of books. For books they also find “exogenous” shocks, things that cause book rankings to change abruptly – a rave review in the New York Times, for instance. From analyzing their data, they find the social network that spreads information about books to be “close to critical”, and that the “exogenous shocks” like rave reviews don’t directly sell many books; the impact is rather in their indirect effect as word of mouth spreads among this complex social network.
For what it’s worth, the full paper title is: “Endogenous Versus Exogenous Shocks in Complex Networks: An Empirical Test Using Book Sale Rankings”.
I wonder how they would classify Oprah’s book club—that seems like both an endogenous word-of-mouth and an exogenous shock. Being selected by Oprah was worth hundreds of thousands in sales and typically made the book into a best-seller.