What Propels A Book To The Top Of Online Sales Charts?

Is the latest bestseller simply the product of clever marketing or has it truly permeated society? Will its popularity wane as quickly as it appeared or will the book be a classic for future generations? Though these questions seem to lay outside the realm of science, scientists can actually obtain deep insights into these issues by using the tools of statistical physics, which can predict the rates at which certain events occur, such as the number of aftershocks following a major earthquake or the number of large avalanches in a given sandpile.

Using a unique database of the Amazon.com rankings of book sales, scientists (Thomas Gilbert, UC-Berkeley, 510-642-5295, tgilbert@haas.berkeley.edu) followed the chart histories of books that reached the top 50 in sales. The researchers found that the bestsellers generally reach their sales peaks in one of two ways, which they classify as "exogenous shocks" (e.g., a rave review in the New York Times) and “endogenous shocks” (e.g., word of mouth). An endogenous shock appears slowly but results in a long-lived growth and decline of sales owing to small but very extensive interactions in the network of buyers.

For example, "The Divine Secrets of the Ya-Ya Sisterhood," reached the bestseller lists two years after it came out (and without a major marketing campaign) by making the rounds of book-discussion clubs and inspiring women to form "Ya-Ya Sisterhood" groups of their own. In contrast, an exogenous shock (rave review) appears suddenly and propels a book to bestseller status; however, these sales typically decline rapidly, much more quickly than those that made the charts via word-of-mouth.

In either case, single triggering events (e.g., a mention on “Oprah”) appear to have much less effect on the sales history of a book than the actions of interconnected groups of people, who may pick up the book after multiple conversations with acquaintances or by hearing about the book secondhand or by remembering a friend's recommendation months or even years after the book comes out.

According to the researchers, marketing agencies could apply their method of classifying and analyzing bestsellers to measure and to maximize the impact of their publicity on the network of potential buyers. (Sornette, Deschatres, Gilbert, and Ageon, Physical Review Letters, 26 November 2004)