The researchers gained free access to a tenth of all tweets, which they ran through an automated language detector. Throwing Twitter languages onto a map revealed highly accurate borders for European countries, a good proof of concept for the effort. On a much smaller scale, Twitter language geography reflected the small pockets of Korean and Russian concentrations within New York City.

　　The Twitter tracking method has its biases. English is the dominant language of the internet, which skews the language distribution in bilingual cities like Montreal. And, obviously, the scientists can't analyze areas where people don't use Twitter. But overall, the study shows that Twitter can provide cheap and useful information. In other words, people tend to speak what they Tweet.