A census is a count and description of a population. Censuses have been taken by the government of France, by individual towns, and by some old provinces. These have been taken primarily for military purposes, taxation, or identification of the poor.
French national censuses have not been microfilmed and are seldom used for genealogical research. Unlike the censuses of the United States, Canada, or Great Britain, they cannot be easily used to locate families. Because French censuses are not indexed, it is not easy to find a name in them. Church records and indexed civil registration are better sources.
The first national census listing names in France was taken in the year 1772. Most national censuses from 1795 to 1836 show only statistics without personal names. From 1836 until 1936, a national census was taken every five years except for 1871 (which was taken in 1872) and 1916 (which was skipped).
Census records less than one hundred years old are confidential and may not be searched by individuals. However, some archivists are not strict with this rule and may allow access to census records up to the last 30 years.
Some earlier censuses may have been destroyed because of an 1887 decree, but this law was not applied everywhere. Early town and provincial censuses usually covered a smaller portion of the local population.
Census records do not consistently give the same information, but after 1836 they usually give the surname and given names, age, occupation, head of house, nationality, and sometimes the birthplace. Use the information with caution, however, since the information may have been given to a census taker by any member of the family or a neighbor. Some information may have been incorrect or deliberately falsified.
National censuses are usually found in the departmental archives. They are not microfilmed by the Family History Library. The early local census records (tax records) of a few towns have been published or microfilmed and are available at the Family History Library. These are listed in the Family History Library Catalog in the Place Search under FRANCE, [DEPARTMENT], [TOWN] - CENSUS.
For more details about French censuses see page 81 of Guide des recherches sur l'histoire des familles.