Science + Technology

UCLA Physicist Applies Physics to Best-Selling Books


Can physics helpexplain what makes a book a best seller?

Yes, says UCLAphysicist and complex systems theorist Didier Sornette, who used statisticalphysics and mathematics to analyze 138 books that made's best-sellerlist between 1997 and April 2004. His team's initial results are published inPhysical Review Letters Nov. 26.

"Complex systemscan be understood, and the book market is a complex system," said Sornette, aprofessor of earth and space sciences, and a member of UCLA's Institute ofGeophysics and Planetary Physics. "Each buyer is not predictable, but complexnetworks have a degree of predictability."

Best-sellingbooks typically reach their sales peaks in one of two ways. The less potent wayis by what Sornette calls an "exogenous shock," which is brief and abrupt. Anexample is "Strong Women Stay Young" by Dr. Miriam Nelson, which peaked on thelist the day after a favorable review in the Sunday New York Times. A secondexample is Sornette's own 2002 book, "Why Stock Markets Crash: Critical Eventsin Complex Financial Systems," which spiked following a favorable review by Jon Markman on CNBC and

"On Jan. 17,2003, my book was ranked 2,000-something and then suddenly it was No. 17," Sornette recalled. "A few hours later,it was in the top 10. As a physicist, it looked to me like an exogenous shockto the system."

Sales aretypically greater, however, when a book benefits from what Sornette calls an"endogenous shock," which progressively accelerates over time, and is illustratedin the book business by favorable word-of-mouth. Such books rise slowly, butthe sales results are more enduring, and the decline in sales is slower andmore much gradual, he found.

An exampleincludes "The Divine Secrets of the Ya-Ya Sisterhood," which reached thebest-seller list two years after it was published, without the benefit of amajor marketing campaign. The book was popular with book clubs and inspiredwomen to form "Ya-Ya Sisterhood" groups of their own. A second example is Nora Roberts'novel, "Heaven and Earth (Three Sisters Island Trilogy)," which peaked onlyafter a slow rise and also fell slowly, which Sornette attributes to word ofthe book spreading among friends and family.

The slower peakstend to generate more sales over time, Sornette said.

"Word-of-mouthcan spread like an epidemic," he said.

The trajectoriesof many books' rankings are combinations of both kinds of peaks, Sornette says,which suggests that an effective, well-timed marketing campaign could combinewith a strong network to enhance sales.

A specialist inthe scientific prediction of catastrophes in a wide range of complex systems,Sornette said his model for analyzing peaks and falls in book sales is verysimilar to one he uses to understand earthquakes. He has applied techniques ofphysics to economic data, and has developed a quantitative model that canpredict the signatures of a coming stock market crash.

"Is it possibleto derive a quantitative law of how book sales behave?" Sornette asks. "We have derived a law of how a sale's shockto the system will jump up and decline over time. The books we analyzed behaved the same way. We can statisticallypredict how the system will evolve, how sales peaks can emerge, and we canpredict the expected decline slope for books that rise sharply."

Sornette hopesthis research will provide insights into complex physical systems, and willshed light on scientific questions in geophysics, biology and climatology.Sornette, who is also a research director at the University of Nice's NationalCenter for Scientific Research in his native France, has written or co-writtenmore than 350 papers in scholarly journals.

Complex systemsin nature experience catastrophic events, such as earthquakes and climatechange, but it can be difficult for scientists to tell whether these events arecaused by natural, internal fluctuations or shocks from external forces.Sornette's team's success in distinguishing between internal and externalcauses suggests that it can be done for other extreme events in complexnetworks as well, he said.,which updates the ranks of its top-selling books each hour, did not participatein this study.

Sornette'sco-authors are Thomas Gilbert, a former UCLA graduate student who is now agraduate student at UC Berkeley's Haas Business School; undergraduate FabriceDeschatres; and Yann Ageon at France's University of Nice.

Sornette's Website is:



Media Contact