There are some 6,909 languages spoken today, but many are on the decline, and the biggest reason, researchers find, is economic growth. Researchers studied the 649 languages for which growth and decline data was available to determine the leading factors driving the change, Science magazine reports. In order to reach their conclusions, they turned to methods typically employed to track endangered animal populations; interestingly, the study's lead author, Tatsuya Amano, is a zoologist.
His team examined the relationships between a language's disappearance and a country's GDP, altitude, and other possible influences. Economic growth showed the strongest correlation to the fading of a language. "As economies develop, one language often comes to dominate a nation's political and educational spheres," Amano says, as per the BBC. "People are forced to adopt the dominant language or risk being left out in the cold—economically and politically." A quarter of the world's languages may be in danger, he notes; fewer than 25 people currently speak Upper Tanana in Alaska, for instance. (Meanwhile, the English language keeps growing.)