Editor's Summary

26 January 2006

Another day another dollar

The website wheresgeorge.com invites its users to enter the serial numbers of their US dollar bills and track them across America and beyond. Why? "For fun and because it had not been done yet", they say. But the dataset accumulated since December 1998 has provided the ideal raw material to test the mathematical laws underlying human travel, and that has important implications for the epidemiology of infectious diseases. Analysis of the trajectories of over half a million dollar bills shows that human dispersal is described by a 'two-parameter continuous-time random walk' model: our travel habits conform to a type of random proliferation known as 'superdiffusion'. And with that much established, it should soon be possible to develop a new class of models to account for the spread of human disease.

Letter: The scaling laws of human travel

D. Brockmann, L. Hufnagel & T. Geisel

doi:10.1038/nature04292

First paragraph | Full Text | PDF (330K) | Supplementary information