Annual

The census is based on an annual collection of information, covering successively all the municipal territories over a period of five years. Municipalities with fewer than 10,000 inhabitants carry out an enumeration of their entire population in one municipality out of five each year. Municipalities of 10,000 inhabitants or more carry out an annual sample survey of a sample of residential buildings representing 8% of their dwellings.

With a total of five surveys, all the inhabitants of municipalities with fewer than 10,000 inhabitants and approximately 40% of the population of municipalities with 10,000 inhabitants or more are taken into account.

Taking all sizes of municipalities together, after 5 years, 70% of dwellings have been covered by a census survey.

The information collected in this way is adjusted to apply to a single date for all municipalities in order to ensure equal treatment between them. This reference date is set at 1 January of the median year of the five survey years in order to obtain more robust data.

The results of the 2021 census are based on the annual census surveys carried out from 2018 to 2023.

Collection begins on the third Thursday in January, except in La Réunion and in Mayotte where it begins two weeks later and in Saint-Pierre-et-Miquelon, where it takes place in March-April.

It lasts a little over four weeks in municipalities with fewer than 10,000 inhabitants and in communities, and a little over five weeks in municipalities with 10,000 inhabitants or more.

The last full enumeration in Mayotte took place in 2017. Mayotte integrated the annual census surveys in 2021 and will be subject to a joint dissemination to the metropolitan territories and other DOMs from the 2023 census.

For each annual survey, the large municipalities follow a two-phase sampling plan in the Address Survey Base (ASB) created from the annual data of the Localised buildings register (RIL).

First phase of sampling:

In metropolitan France, the residential buildings (or addressed entities) were divided into five rotation groups by balanced random draw. The drawing of the sample of buildings from a given ACS mobilises only one of the five rotation groups, by rotation. The constitution of the buildings rotation groups constitutes the first phase of the draw.

In the French overseas departments, each large municipality was partitioned into several sets of contiguous buildings known as << îlots >>. In each municipality, the << îlots >> were divided into five rotation groups. The constitution of the rotation groups constitutes in this context the first phase of the draw.

Second draw phase:

Addressed entities belonging to the strata of large buildings, new buildings and tourist establishments are exhaustively enumerated. The buildings belonging to the stratum of known small addresses are selected in such a way as to obtain 40% of the dwellings surveyed in the annual rotation group.

Over a 5-year cycle, 26 million dwellings and 48 million people are enumerated.

The individual form covers the characteristics of the individual: sex, age, marital status, place of birth, nationality, place of study, diplomas, place of previous residence (one year before), employment, social category, economic activity sector, workplace, etc.

The housing form describes the characteristics of:

• The household: composition, size, family ties, number of cars, etc.;

• The dwelling: type, year of completion, size, type of occupation, public housing, heating, bathroom, sewage disposal, year of moving in, parking, etc.

The forms (individual , individual for communities, housing for metropolitan France and the DOM) as well as the explanatory notes are available on the website  "le recensement et moi" (site updated at each ACS).

A census year is created from five annual census surveys for the calculation of legal populations.

In municipalities of 10,000 inhabitants or more, where census surveys are carried out every year by sampling: the principle of the calculation is to calculate an average number of people per dwelling over the last five years, then deducting the entire municipality by referring to the number of dwellings in the middle of the period, as known by the localized building register (Ril).

In municipalities with fewer than 10,000 inhabitants, INSEE determines the legal populations by extrapolation or interpolation of the results obtained by the most recent census survey. In the case of extrapolation, these calculations consist of extending observed trends based on the number of dwellings provided by the tax data, and in the case of interpolation, establishing intermediate figures between two years for which the populations are known.

The first phase of statistical analysis , known as the main processing, concerns all the questionnaires collected. It produces a detailed file containing all the dwellings and individuals surveyed. The main processing deals with all the information that can be easily coded after the data capture of the paper questionnaires.

The statistical results of this operation cover most of the fields of study allowed by the census questionnaires (individual and dwelling form), which are classified into 7 themes on insee.fr:

• Evolution and structure of the population (age, sex, etc.);
• Couples-Families-Households (marital status, living with a partner, household size, etc.);
• Dwellings (category and type of dwelling, period of completion, occupancy status, number of rooms, length of time since moving in, etc.)- Residential migration (place of residence 1 year earlier);
• Diplomas-Training-School mobility (schooling and place of study, highest diploma, etc.);
• Labour force, Employment,Unemployment (activity rate by sex and age, active people in employment, unemployment according to the census, etc.);
• Employment characteristics - Professional mobility (professional status, employment conditions, part-time work, place of work, mode of transport to work...);
• Foreigners-Immigrants (distinction between French/foreigners and immigrants/non-immigrants by gender and age).

The second phase of the statistical processing , called complementary, is intended to produce variables whose elaboration is more complex.

These are those that describe:

• The family structure of households: precise determination of the reference person of the household, identification, if necessary, of families within the household and composition of these families;

• The sectors of activity in which the jobs are carried out;

• The occupation and socio-professional category of people.

Since the 2014 survey, one fith of households

in municipalities with fewer than 10,000 inhabitants have been included in the supplementary survey, and all household questionnaires (i.e. around 40%) in municipalities with 10,000 inhabitants or more. For all communes, the complementary analysis also covers one individual in 5 communities.

not applicable