How Fast Can Word Travel?

A look at the results of two mathematic professors' experiment studying how fast a rumor can spread on-line.

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Word of mouth about a product that once would have taken six months to get through a community of actual and potential customers can now race through an on-line population via E-mail.

Steve Abbott and Bill Peterson, both assistant professors of mathematics at Middlebury College, in Middlebury, Vt., assigned an E-mail problem to a group of students, namely, Bongani Dlamini, Grant Gibson, Paul Holmes à Court, Laura Tabor, and Douglas Tisdahl.

The students spent a month spinning equations, building computer models, even planting E-mail messages in the college system to discover how long information takes to circulate. The answer they churned out varied, depending on several factors: how many people initially -- and eventually -- received the message, how often people checked their E-mail, and how many people were in the population. Take, for example, a population of about 1,600 users (a plausible number of on-line customers for a smallish company), each of whom checks his or her E-mail twice a day. If one person sends a message to two people, with an average number of forwardings of about 1.5 per message (which means one out of two people sends out three copies), in about six days half the population would have received the message.

In any case, companies subject to Internet gossip clearly don't have to wait as long as they used to for the good word to get out -- or for the slings and arrows of outrageous flaming to hit home .

-- David H. Freedman

David H. Freedman: A Boston-based contributing editor, Freedman is the co-author of A Perfect Mess, which examines the useful role of disorder in daily life, business, and science. @dhfreedman