Cell phone companies are finding that they’re sitting on a gold mine–in the form of the call records of their subscribers.
Researchers in academia, and increasingly within the mobile industry, are working with large databases showing where and when calls and texts are made and received to reveal commuting habits, how far people travel for public events, and even significant social trends.
With potential applications ranging from city planning to marketing, such studies could also provide a new source of revenue for the cell phone companies. “Because cell phones have become so ubiquitous, mining the data they generate can really revolutionize the study of human behavior,” says Ramón Cáceres, a lead researcher at AT&T’s research labs in Florham Park, NJ.
If you were an AT&T subscriber and were near Los Angeles or New York between March 15 and May 15 last year, there’s a 5 percent chance that your data was crunched by Cáceres and his colleagues in a study of the travel habits of the company’s subscribers. The researchers amassed millions of call records from hundreds of thousands of users in 891 zip codes, covering every New York borough, 10 New Jersey counties, as well as Los Angeles, Orange, and Ventura counties in California.
The data set is a collection of call detail records, or CDRs–the standard feedstock of cell phone data mining. A CDR is generated for every voice or SMS connection. Among other things, it shows the origin and destination number, the type and duration of connection, and, most crucially, the unique ID of the cell tower a handset was connected to when a connection was made.
That let the AT&T team know the location of a phone to within a mile radius at the time each CDR was generated, making it possible to determine the distance traveled from home by each cell phone every day. The group found that, on average, people living in Manhattan travel 2.5 miles most days, compared to five miles in Los Angeles. “But we also found that when you look at the longest trips people make, people that live in New York go significantly further, 69 miles on a weekday compared to 29 in Los Angeles,” Cáceres says.
Cáceres hopes to work with city planners, who would usually have to resort to expensive and limited surveys to gather such information. “This kind of data can help them decide how to invest resources, for example if they want to know where to build a new train or subway station,” he says. The AT&T work was presented at a recent workshop in Cambridge, MA, earlier this month as part of the NetSci conference on network science.