Step 3 The Age of Migration

Although a common phenomenon, this personal multilingualism or plurilingualism has been given added importance and a new focus by the mass migrations of the 20th century, in particular in countries which have been the destination for migrants, such as the countries of Europe.  
You can learn more about this by reading this text entitled ‘The Age of Migration’ which is an extract from Languages in Europe towards 2000 p. 27/8, which refers to the work of Castles and Miller - The Age of Migration (2009)