Study secretly tracked 100.000 cellphone users' locations

Source: Northeastern University

Researchers secretly tracked the locations of 100.000 people outside the United States through their cellphone 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 3/4 of those studied mainly stayed within a 20-mile-wide circle for half a year. The study found that nearly half of the people in the study pretty much keep to a circle little more than 6 miles wide and that 83% of the people tracked mostly stay within a 37-mile wide circle. But then there are the people who are the travel equivalent of the super-rich, said Hidalgo, who travels more than 150 miles every weekend to visit his girlfriend. Nearly 3% of the population regularly go beyond a 200-mile wide circle. Less than 1% of people travel often out of a 621-mile circle. But most people like to stay much closer to home. Hidalgo said he understands why: "There's a lot of people who don't like hectic lives. Travel is such a hassle."

The scientists would not say where the study was done, only describing the location as an industrialized nation.

Researchers used cellphone 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 cellphones 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 cellphone 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.

The study, to be published Thursday in the journal Nature, opens up the field of human-tracking for science and calls attention to what experts said is an emerging issue of locational privacy. "This is a new step for science," said study co-author Albert-Lazlo Barabasi, director of Northeastern's Center for Complex Network Research. "For the first time we have a chance to really objectively follow certain aspects of human behavior."

Barabasi said he spent nearly half his time on the study worrying about privacy issues. Researchers didn't know which phone numbers were involved. They were not able to say precisely where people were, just which nearby cell phone tower was relaying the calls, which could be a matter of blocks or miles. They started with 6 million phone numbers and chose the 100.000 at random to provide "an extra layer" of anonymity for the research subjects, he said.