"Stockbrokers may act like sheep," by Mark Haw. Nature Science Update, 3 January 2001.
Haw describes a computer simulation by Victor Eguiluz and Martin Zimmerman that attempts to model the stock market. Eguiluz and Zimmerman programmed into their model the fact that brokers network. The results of the simulation showed a power law in the returns on investments. Actual stock market returns also follow a power law. "This, they argue, shows that the power law in the market statistics could be explained by copycat behaviour amongst brokers," Haw writes. Haw's article can be found at http://www.nature.com/nsu/010104/010104-1.html. It summarizes Eguiluz' and Zimmerman's article: "Transmission of information and herd behaviour: an application to financial markets" which appears in the journal Physical Review Letters, 85, pp. 56595662 (2000).
--- Michael Breen