INEbase / Demography and Population / Population Figures and Demographic Censuses / Population and Housing Census 2001

Population and Housing Census 2001

Frequently Asked Questions

What are Population Censuses?  Top

They are comprehensive population counts that the Statistics Offices are required to carry out periodically by law, normally every ten years, to identify the social and demographic characteristics of the inhabitants.

The first modern population census, considering "all inhabitants" as the unit under study, was performed in Spain in 1768 by the Count of Aranda, under the rule of King Charles III; however the first Official Census dates back to 1857. The last census was performed using November 1st 2001 as the reference date.

Housing Censuses are carried out at the same time as the Population Censuses, as this allows the characteristics of the inhabitants to be linked to the dwellings they inhabit.

Why do we need Population and Housing Censuses?  Top

Censuses are carried out for many reasons. The census information can provide conclusions as important as:

  • How many people live in Spain and How they are distributed by sex, age, place of birth, marital status, place of residence, etc.
  • How households are structured at present, considering different forms of coexistence.
  • The number of persons who are working, which can be classified by activities, by professional situation, and by the number of persons who are unemployed and those are seeking employment. Equally, the number of persons that are studying and the sector or the studies they have accomplished.
  • The number of daily journeys and means of transport used to go to work or to the place of study.
  • Characteristics of the dwellings, the buildings and the premises.
  • The problems or deficiencies these viviendas and the environment present, eand the type of facilities (lift, etc.), etc.
  • Availability of a second dwelling.

This information can be used to plan policies regarding demography, health, education, assistance, environment, etc. as well as the assess the results of these measures.

Furthermore, since the Census collects all the information on the population resident in the Spanish territory, it can:

  • Act as the framework for surveys performed by the INE by sampling and for the selection of statistical units (census sections, municipalities, blocks).
  • Allocate economic resources from the State and the European Union to Autonomous Communities and Councils for rural development, the construction of roads, etc.

Who compiles the Censuses in Spain? Who is responsible?  Top

Population and housing censuses are carried out by the National Statistics Institute. However, many persons and organisations take part in the design and content of the censuses, either direct or indirectly.

The first ideas on the approach for the 2001 Census, as well as the draft census project, were distributed to the Central and the Autonomic Administration, researchers and business and union organisations, and the suggestions made by them all were considered when drafting the final Project.

Councils and, to a certain extent, the Autonomous Communities' Statistical Institutions take part in the execution of the Censuses.

Who uses the Censuses? How?  Top

Many and very different people demand census information. From the Administration to companies, trade unions, researchers, students and the citizens in general, they all request information, sometimes in more detailed manner than advertised. All queries are answered, bearing in mind one single limitation: to preserve statistical secrecy.

In general, they are used by all persons who are responsible for planning social and economic projects or by persons who wish to assess the results of said projects.

Does the Census include all the Spanish population or are certain groups excluded?  Top

The 2001 Census gathers information on all the population whose regular residence is located in the national territory, that is, not only the Spanish population, but also the foreign population resident in Spain, regardless of whether they have a work permit or of any other characteristic.

In order to collect this information, interviewers have visited family dwellings, accommodations (caves, shacks, wagons, etc.) and group dwellings (convents, nursing homes, etc.). The Census even includes people without a fixed address as long as they have some kind of address, for example a social assistance centre.

Why carry out Censuses when the INE performs specific surveys that can provide the same information?  Top

In fact, the National Statistics Institute performs a wide variety of surveys that serve very different purposes. For example:

  • to analyse unemployed or employed persons, the INE performs the Active Population Survey (APS).
  • to study the consumption in households of goods and services, the INE performs the Household Budgets Survey.
  • to identify the behaviour of women towards fertility, the INE performs the Fertility Survey.
  • to identify the number of persons who have a physical or mental limitation, the INE performs the Survey on Disabilities, Impairments and Health Status, etc.

Furthermore, these surveys that study specific issues can provide much more in-depth information, presenting data on numerous auxiliary variables.

The characteristics are only studied for a representative sample of the population, which imposes certain limitations when providing information for reduced areas or groups, as the values become unrepresentative when below a specific population level.

However, the Population Census, although it is a less in-depth operation, given its exhaustive character, pprovides results at any level of breakdown with the only limit established being the protection of statistical secrecy.

What differences are there between the Population Census and the Municipal register?  Top

Although both collect information on the same inhabitants, they differ in purpose and content.

Indeed, the Population Census has a statistical nature and its goal is to provide information on the number and distribution of the main demographic and social characteristics, always respecting statistical secrecy. On the other hand, the purpose of the Register is purely administrative, to accredit a person resides at a certain domicile. Therefore the information is nominal.

The Register's information is established in the Law on the Basis of Local Regimes, which limits the information to name and surname, ID number, address, sex, place and date of birth, nationality and school or academic education of the persons resident in the municipality. On the contrary, the Population census contains much more information; for example, marital status, economic activity, conditions of the dwelling, type of transport used to get to work, relationship between household members, etc.

The Population Census provides a snapshot of society at the time it is carried out and cannot be updated in any manner. After completing the operations that involve collecting and controlling the census information, the data that could allow the direct identification of the persons are removed: name and surname and ID number, as this information is not needed for statistical purposes and, furthermore, eliminating these variables strengthens the protection of the statistical secrecy. The register is constantly updated when people are born, change their characteristics (address, level of education, etc.) or pass away.

Is there a connection between the Municipal Register and the Population Census?  Top

The Census and the Register use the same residence concept. Therefore persons must use their regular address in the Census, since -in all- that is the place where they should reside according to the Register. In the extreme case of a person who has several addresses, they should only be registered in the Census in the address where they spend most of the year, as this is the criterion used in the Register.

So as to make things easier for the citizens, the 2001 Census includes the Register information the INE has accessed that has been printed beforehand on the census questionnaires. This prevents citizens having to provide the information the INE and the Councils already have.

Moreover, it has also been a way to ensure citizens update their Register information. The INE will be in charge of channeling these proposed changes to the Councils so as to avoid, as much as possible, citizens having to go to the municipal venues to update their personal data.

Can the Municipal Register replace the Population Census?  Top

They are two complementary sources given that although they both collect information on the same inhabitants, they differ in their purpose and content.

As aforementioned, the Population Census provides information on many more variables than the Municipal Register, whose content is governed by the valid legislation. The Population Census does not keep information such as the name, surname or ID number so as to protect statistical secrecy, whilst the Municipal Register does to fulfil its purposes as an administrative register.

Finally, the Population Census is a snapshot of the population at a certain moment in time that is only updated every ten years, whilst the Municipal Register is constantly updated showing registrations, deletions and modifications.

What connection is there between the Electoral Census, the Municipal Register and the Population Census?  Top

The Electoral Census is a record of the population aged 16 years old or older, compiled for use when electoral processes are called. It contains information on the Spaniards residents in Spain (CER), Spaniards resident abroad (CERA) and foreigners resident in Spain that have the right to vote in elections to the European Parliament, or in municipal elections.

The Electoral Census is updated monthly via the information provided by Councils, Consulates and Civil Registers. Its existence is regulated by the General Organic Electoral Law (GOEL) and is managed by the Electoral Census Office, part of the National Statistics Institute, supervised and directed by the Central Electoral Board.

Thus, the Electoral Census gathers a subgroup of the population included in the Municipal Registers. They both use similar updating sources and, therefore, despite being regulated by different norms, they present a high level of coincidence.

As occurs with registers, the Electoral Census is also updated continuously and includes a very limited amount of information: the data needed to establish the citizen's right to vote in electoral processes. The Population Census is a totally different operation, as it is a snapshot of the population with a specific reference date, obtained via the collection of questionnaires that covers certain fields of interest and where the information is protected by statistical secrecy.

How much did the 2001 Population Census cost?  Top

In general, the cost of any statistical research depends essentially on the number of units that must provide information. As regards the Population Census, these units are each and every one of the citizens living in Spain at a certain moment.

Thus, the Population Census becomes the largest statistical operation performed by Statistical Offices.

The budget for 2001 Demographic Censuses (population, dwellings and buildings) amounts to 27,500 million pesetas, of which 69% corresponds to personnel expenses. Other important budget items are: computer processing of the information (5% of the total), publishing the questionnaires and the rest of the census material (5% of the total), and the infrastructures used to create premises for census offices (another 5% of the total).

How many Census agents were hired?  Top

In order to perform statistical work, the national territory is divided into census sections. There are 33,000 census sections in total. In general, each section is carried out by one agent, although in some cases one same agent can be responsible for two or more sections and in others, given the size or difficulty, more than one agent is responsible for a single section. There were 35,000 agents in total.

As well as agents, there were also 5,500 group directors who controlled the work of several agents. Auxiliary personnel was hired to carry out office work. The personnel hired amounted to 42,500 in total.

Which are the most important innovations included in the 2001 Censuses compared to the previous ones?  Top

The first characteristic of the 2001 Census compared to previous ones is the long process during which the census project has been developed. In June 1996, after the dissemination of the 1991 Census results, the INE prepared a document entitled "Reflections on the 2001 Demographic Census," exposing the approaches that would be used in the different stages of the next Census, in view of the experience obtained from the previous Census.

As regards the actual Census Project, it is important to note that in 2001, a single plan was established for all Demographic Censuses (Population, Dwellings and Buildings), thus involving economic savings and making it easier to include the information from the different Censuses, given that in previous one, the Building Census was performed a year before and was used as the starting point for the Population and Dwellings censuses.

For the 2001 Census, the infrastructure was obtained using two relevant administrative files: The Register and the Cadastre The former provided the location of the buildings containing main dwellings (in which there were people who resided there regularly) and the latter allowed the identification of the other buildings (buildings without resident persons and commercial premises).

On the other hand, as aforementioned, the 2001 operation used personalised questionnaires with the Register information and the information collected was captured via optical reading systems using high performance scanners. Subsequently, scanned imaged were processed using OCR techniques. Thus, the information was available for automatic coding via the corresponding dictionaries.

In order to make it easier to scan the questionnaires and the make this stage as short as possible, the questionnaires were designed in a DIN-A4 size, which is more efficient.

Another important innovation included in the 2001 Censuses is that the cumplimentación de los cuestionarios por Internet. The INE is a global pioneer in the use of this system, as these are the first censuses that have offered all the population the possibility of completing them via the Internet.

However, the most important innovation of the Censuses is that agents have provided each dwelling with a personalised questionnaire, whilst in previous Censuses any questionnaire could be provided to any dwelling, as they were all identical.

It also important to note that, although the printing of the questionnaires has always been a critical stage in all census operation, especially given the volume and difficulty of the distribution, in the 2001 Censuses these problems have increased given the requirements of this personalisation.

Which questionnaires did respondents have to complete for the 2001 Population and Housing Census?   Top

The 2001 Census operation included four models of questionnaires, although not all the persons resident in the dwellings had to complete them. The following documents were used:

  1. Register information. This document verified if the information the Councils have in the Register, which printed on this sheet, is correct.
  2. Dwelling Questionnaire. This questionnaire garners the most important characteristics of main dwellings (those where a person lives regularly).
  3. Household questionnaire. Gathering census variables that have to be completed by all persons (marital status, type of studies, municipality of residence on March 1st 1991, etc.).
  4. Individual questionnaire. Only completed by persons aged 16 years old or older who study or work. Containing information on the type of work or studies, and the place where they are carried out.

How were queries regarding answering the questionnaire solved?  Top

Three channels:

  1. Free-phone number
  2. Website:
  3. Asking the census agent when they visited the dwelling to collect the questionnaire.

How did the questionnaires reach each household?  Top

The census agents visited each address handing out the questionnaires that had to be completed by the residents. The census questionnaires for each household were provided grouped together in the same envelope.

The rule established that census agents were to hand the document to household member in person. However, if this was not possible for a given reason, the agents used a closed envelope This protected the privacy of the personal information.

When providing the questionnaires, the census agent answered all queries the citizens had regarding completing the documents and even filled them in him/herself when none of the household members were able to do so.

The census agent informed the household members of when he/she would collect the questionnaires. Furthermore, a poster was left in the building entrance indicating the day the questionnaires would be collected from each of the dwellings in the building. If on the day the information would be collected, no household members were available, they could leave the questionnaires with a trustworthy person in the same closed envelope in which they were received.

Did the agents have specific identification?  Top

The agents were provided with a personal ID card that identified them as National Statistics Institute personnel, which they were requested to show when providing and collecting questionnaires.

This card required they fulfil the obligations of the census agents and, especially, the obligation of protecting the secrecy of all individual information related to the census operation. Several penalties were established to sanction cases of non-compliance.

What confidentiality guarantees are applicable to the information the citizens provided in the Censuses?  Top

The data collected in the actual census questionnaires (dwelling, household and individual questionnaires) will never be disseminated with a nominal character , as the data is protected by statistical secrecy, and the dissemination of the results will not enable the identification of the reference person.

Statistical secrecy ensures that no private company or public administration will be able to identify personal details provided by the citizens in the census, with the exception of the modifications regarding the register information, which are sent to the corresponding Councils, to allow them to update the Municipal Register.