It should be noted that the French Census is not a traditional one, but instead it's a mix of a traditional one, a register-based and extrapolated one on a rolling basis. From Germany's 2011 Census page on the methods of the 2011 Censuses in Europe:
Rolling census in France
"In France it is planned to apply a method which is unique in Europe: With a rolling system, data are collected only from part of the population every year. Within a survey cycle of five years, a full census will be conducted in the municipalities with less than 10,000 inhabitants; in municipalities with 10,000 inhabitants and more, only sample surveys will be conducted, covering about 40 percent of the municipality’s inhabitants. As half of the French live in smaller municipalities, some 70 percent of the population will entirely be covered with this method. For the remaining 30 percent, expansions will be required. The first publication of a population figure based on the new method is scheduled for 2008, referring to 2006. Then, annual results will be available."
http://www.zensus2011.de/Statistik-Portal/en/Zensus/en_zensenA.asp
