The 2021 Population and Housing Census is the eighteenth of the official censuses carried out in Spain. Unlike previous censuses, the 2021 Census was not constructed by collecting information from household interviews. For the first time, it was prepared by combining dozens of administrative records.

Spain thus joins the small group of countries that have managed to construct population censuses from administrative records, which is considered the highest quality and most efficient method.

The census operation has resulted in a set of files with individual data:

• a complete file of people made up of as many records as inhabitants on January 1, 2021, the census reference date. It contains the demographic characteristics, studies, employment situation, and migrations of the entire population.
• a complete file of households with information on household composition and size.
• a complete file of collective establishments showing their population and the type of collective.
• a complete file of dwellings, with information on the surface, year of construction, tenancy regime of the dwelling, etc.

The constructed product is thus based on microdata that collects information from the entire population. In other words, it is an exhaustive census, similar to what would be obtained if questionnaires for all Spanish households were processed using a classic census.

In addition, this demographic information production system, based on administrative records, ends decennial census publication, as has occurred without interruption since 1857. This 2021 edition inaugurates the start of annual censuses.