About 75% of the population live in urban areas. Until the end of World War II the population increase in France was perhaps the lowest in Europe, but in postwar decades the rate has increased. The mingling of peoples over the centuries as well as immigration in the 20th cent. has given France great ethnic diversity. A large influx of predominantly North African immigrants has had a great effect on the cities, especially Paris and Marseille.
French is the nation's language. There are also a number of regional dialects, which are largely declining in usage. Alsatian, a German dialect, is spoken in Alsace and in parts of Lorraine. A small number speak Flemish, a Dutch dialect, in French Flanders. In Celtic Brittany, Breton is still spoken, as is Basque in the Bayonne region, Provençal in Provence, Catalan at the eastern end of the Pyrenees, and Corsican on the island of Corsica.
Roman Catholicism is by far the largest religion in France, nominally professed by about 85% of the population, although only an estimated 5% are churchgoers. With growing immigration from Asia, Turkey, and North Africa, France also has a large Muslim population, estimated at 3 to 5 million. There are smaller numbers of Protestants and Jews. Separation of church and state was made final by law in 1905.