9 languages for 90% of the world’s population

"To engage with all but a tiny fraction of people in the world, you definitely do not need to learn all their first languages. You need to learn all their vehicular languages – languages learned by nonnative speakers for the purpose of communicating with native speakers of a third tongue. There are about eighty languages used in this way in some part of the world. But because vehicular languages are also native to some (usually very large) groups, and because many people speak more than one vehicular language (of which one may or may not be native to them), you do not need to learn all eighty vehicular languages to communicate with most people on the planet. Knowing just nine of them – Chinese (with 1.3 billion users), Hindi (800 million), Arabic (530 million), Spanish (350 million), Russian (278 million), Urdu (180 million), French (175 million), Japanese (130 million), and English (somewhere between 800 million and 1.8 billion) – would permit effective everyday conversation, though probably not detailed negotation or serious intellectual debate, with at least 4.5 billion and maybe up to 5.5 billion people, that is to say, around 90 percent of the world’s population." (David Bellos, Is that a fish in your ear? Translation and the meaning of everything, p14)