Paris is divided into 20 arrondissements (districts or boroughs), each of which has a local council and a mayor, but most of the power is held by the mayor of the City of Paris who is chosen by the city's council. Paris and its suburbs together make up the eight departments of the Île-de-France administrative region, which is governed by an elected assembly, chairman (or president), and supervisor and overseen by a prefect appointed by the state.
Immigrants to France now constitute nearly 20% of Paris's population. The majority of these are Algerian, Moroccan, and Tunisian. Large groups of Indochinese have also immigrated to Paris. About 75% of all Parisians live in the suburbs due to high costs and a high population density in the city. New towns have been built, consolidating suburban areas, and a great deal of manufacturing and other industry takes place in the suburbs.