Nature has published this study (subcription required) by researchers at Northeastern U:
Despite their importance for urban planning, traffic forecasting and the spread of biological and mobile viruses, our understanding of the basic laws governing human motion remains limited owing to the lack of tools to monitor the time-resolved location of individuals. Here we study the trajectory of 100,000 anonymized mobile phone users whose position is tracked for a six-month period. We find that, in contrast with the random trajectories predicted by the prevailing Lévy flight and random walk models, human trajectories show a high degree of temporal and spatial regularity, each individual being characterized by a time-independent characteristic travel distance and a significant probability to return to a few highly frequented locations. After correcting for differences in travel distances and the inherent anisotropy of each trajectory, the individual travel patterns collapse into a single spatial probability distribution, indicating that, despite the diversity of their travel history, humans follow simple reproducible patterns. This inherent similarity in travel patterns could impact all phenomena driven by human mobility, from epidemic prevention to emergency response, urban planning and agent-based modelling.
In addition to its findings, this study is remarkable in that it would be illegal if conducted in the US, as Wired News notes here:
Researchers secretly tracked the locations of 100,000 people outside the United States through their cell phone use and concluded that most people rarely stray more than a few miles from home.
The first-of-its-kind study by Northeastern University raises privacy and ethical questions for its monitoring methods, which would be illegal in the United States.
It also yielded somewhat surprising results that reveal how little people move around in their daily lives. Nearly three-quarters of those studied mainly stayed within a 20-mile-wide circle for half a year.
The scientists would not say where the study was done, only describing the location as an industrialized nation.
Researchers used cell phone towers to track individuals’ locations whenever they made or received phone calls and text messages over six months. In a second set of records, researchers took another 206 cell phones that had tracking devices in them and got records for their locations every two hours over a week’s time period.
The study was based on cell phone records from a private company, whose name also was not disclosed.
Study co-author Cesar Hidalgo, a physics researcher at Northeastern, said he and his colleagues didn’t know the individual phone numbers because they were disguised into “ugly” 26-digit-and-letter codes.
That type of nonconsensual tracking would be illegal in the United States, according to Rob Kenny, a spokesman for the Federal Communications Commission. Consensual tracking, however, is legal and even marketed as a special feature by some U.S. cell phone providers.