Post written by François Grosjean.
Whenever I give a talk on bilingualism, I surprise my audience with the following estimate: more than half of the world's population uses two or more languages (or dialects) in everyday life. Bilingualism is present on all continents, in all classes of society, in all age groups.
We know, for example, that in Asia and Africa, many people are bi- or multilingual although precise figures are often lacking. (See here for a discussion on the difficulty of counting bilinguals). In Europe, a bit more than half of the population is at least bilingual. Smaller countries such as Luxembourg, Switzerland, and The Netherlands house many bilinguals whereas larger countries such as Great Britain and France have fewer of them.
In North America, some 35% of the population in Canada is bilingual and although the percentage is smaller in the United States - close to 20% - this still corresponds to an estimated 55 million inhabitants. Bilingualism in the US is very diverse, pairing English with Native American languages, older colonial languages, recent immigration languages, and so on (see here).
How can one explain such large numbers of bilinguals? One reason is simply that many countries house numerous languages: 722 in Indonesia, 445 in India, 207 in Australia and so on. Contact between communities means learning other languages or, at the very least, acquiring a common language of communication and hence being bilingual.
In addition, some countries have a language policy that recognizes and fosters several languages - at the very least their official or national languages. Children learn these languages (or some of them) and many may well be educated in a language that is not their native language.
Trade and business are a major cause of language contact and hence bilingualism. For example, Greek was the language of buyers and sellers in the Mediterranean during the third, fourth and fifth centuries BCE and, of course, English has become a major language of trade and business today. I have known business people in Sweden, Switzerland and Singapore who speak English all day at work and return home to speak their native language.
An important cause of bilingualism is the movement of peoples. The reasons are many - political, religious, social, economic - and go back to the beginning to time. For instance, people have always moved to other regions or countries in search of work and better living conditions, and this has led to substantial bilingualism. It is with this in mind that American linguist Einar Haugen, a pioneer of bilingualism studies, stated that the United States has probably been the home of more bilingual speakers than any other country in the world.
This said, bilingualism is not very extensive at any one time in the US since it is basically short-lived and transitional. For generations and generations of Americans, bilingualism has covered a brief period, spanning one or two generations, between monolingualism in a minority language and monolingualism in English.
Things may be changing though. An increasing number of families are fostering bilingualism by encouraging their children to learn two languages, English and another language, very often the home language. Many are thereby keeping their linguistic and cultural heritage alive in addition to giving their children the possibility of knowing another language.
An increasing number of professions need people who speak two or more languages. In addition, bilingualism allows you to communicate with different people and hence to discover different cultures, thereby giving you a different perspective on the world.
Reference: "Why are people bilingual?". Chapter 1 of Grosjean, François (2010). Bilingual: Life and Reality. Cambridge, Mass: Harvard University Press.
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François Grosjean's website: www.francoisgrosjean.ch