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Population and Housing Census 2001

2001 Census via Internet

In order to provide citizens with another form of completing the Census questionnaires, the INE implemented a mechanism that allowed respondents to use the Internet, as an added possibility to the traditional collection of documents on paper.

Only three countries have performed similar experiences to date, albeit with a smaller scope than the Spanish one:

  • Singapore offered 20% of the population (the sample part of the census) the possibility of completing the Census via the Internet in 2000.
  • The US also offered this possibility in their 2000 Census, although only for a limited part of the addressees answering their so-called short questionnaire.
  • Finally, the most similar operation was carried out in Switzerland, where inhabitants living in communes (councils) that subcontracted (via compensatory payment) the execution of the Census to a Federal Statistical Office were able to complete the documentation via the Internet. This applied to 60% of the communes, leaving 10% of the population outside the possibility of completing the Census via the Internet.

Thus, Spain was the first country in the world to allow all persons registered in the same dwelling where they actually reside to complete the Census via the Internet.

The questionnaires that were distributed to the population on paper included information that had been printed beforehand in accordance with the register information available at the INE. If an error or omission were detected in the pre-printed information, users were required to be in possession of a digital certificate (electronic digital signature so as to modify them. However, the citizens that considered the pre-printed information was correct could complete the Census information via the Internet immediately, using the established authentication procedure which is described briefly hereunder:

  1. Two passwords printed on the questionnaire.
  2. The ID number (DNI) of the one of the persons included in the Census questionnaire (this ID number is also already printed on the questionnaire), and
  3. The name of the mother and the father as they appear on the ID card of the household member (this information is not already printed on the Census questionnaire).

Other authentication procedures were also used, such as systems to control incorrect accesses, anti-fraud measures, etc

Thus, in order to complete the Census via the Internet, users had to receive the Census envelope at the address where they resided and follow the instructions included, by connecting to

The system allowed the users to interrupt the process of completing the questionnaire and continue it subsequently. When the questionnaire had been completed correctly, the system provided the user with a number that would act as the receipt or the proof that said questionnaire had been filled in completely.

In order to make things easier for the citizens, persons with visual impairments or other disabilities who found it hard to use a computer were given the possibility of completing the Population Census via the Internet.

Furthermore, the aforementioned server allowed questionnaires to be completed in Spanish and in the co-official languages used in bilingual autonomous communities. Questionnaires were also available in some foreign languages (English, French, German and Arabic).

Another advantage of collecting the information via the Internet was the inclusion of a series of rules regarding editing the questionnaire in a Web format; that is, a series of rules to be followed to guarantee the quality and consistency of each of the questionnaires completed via the Internet. Each user completing the questionnaire via the Internet had to be informed at all times of the emergence of any problems that prevented the final acceptance of the questionnaire, so that the users could correct the corresponding errors.

An "immediate payment" mechanism was created to award respondents who completed the documentation via the Internet, consisting in the automatic and immediate provision (after completing the questionnaire correctly via the Internet) of information regarding the frequency of the surname requested by the respondent in a certain province (one per dwelling; the surname did not necessarily have to be that of person) using information from the register itself, complying to the appropriate rules to respect statistical secrecy.

During the period the census was underway, a call-centre was set up to solve all the queries that could arise regarding completing a Census questionnaire via the Internet and on paper.

The Internet operation was coordinated with the collection of the documents on paper, which was controlled from the Regional Offices so that no Census agent could claim questionnaires that had been completed previously via the Internet.

The software used is known as three-tier software:

  • Presentation tier / User interface.
  • Web server and applications.
  • Databases

The process used state-of-the-art software technology, which satisfied the requirements for quality, flexibility, scalability, reliability and security.

Finally, the protection system was composed by different measures (firewalls, etc.) that would strictly guarantee compliance with the legislation as regards statistical secrecy and data protection.

Results of the collection via the Internet

The number of households that decided to use the possibility of completing the Census via the Internet was not very high (13,768). The reasons for this low share have not yet been analysed. In any case, the National Statistics Institute has fulfilled its objective of offering the citizens this possibility.

By Autonomous Communities, of every 10,000 households, the Census was completed via the Internet
Comunidad de Madrid 29.1   Comunidad Foral de Navarra 7.0
Comunidad de Aragón 11.2   Comunidad de Castilla y León 5.5
Comunidad de Cataluña 10.8   Comunidad de Andalucía 5.1
Total de España: 9.7   Comunidad de Galicia 4.7
Comunidad de Rioja(La) 9.6   Comunidad de Baleares(Islas) 4.5
Comunidad del Principado de Asturias 9.1   Comunidad de Castilla-La Mancha 4.0
Comunidad del País Vasco 8.7   Comunidad de Murcia(Región de) 3.3
Ceuta y Melilla 8.5   Comunidad de Canarias 3.3
Comunidad de Cantabria 7.5   Comunidad de Extremadura 2.7
Comunitat Valenciana 7.4      

By provinces, of every 10,000 households, the Census was completed via the Internet
Madrid 29   Navarra 7   Alicante/Alacant 4
Álava 15   Málaga 7   Segovia 3
Zaragoza 13   Tarragona 7   Cuenca 3
Guadalajara 13   Burgos 6   Murcia 3
Barcelona 12   Salamanca 6   León 3
Ceuta 12   Palencia 5   Pontevedra 3
Valladolid 10   Cádiz 5   Cáceres 3
Total de España 10   Melilla 5   Teruel 3
Valencia/València 10   Guipúzcoa 5   Zamora 3
Rioja (La) 10   Girona 5   Badajoz 3
Vizcaya 9   Granada 5   Almería 3
Asturias 9   Ávila 4   Santa Cruz de Tenerife 2
Castellón/Castelló 9   Balears (Illes) 4   Lugo 2
Huesca 9   Palmas (Las) 4   Jaén 2
Cantabria 8   Toledo 4   Huelva 2
Sevilla 7   Albacete 4   Soria 2
Lleida 7   Córdoba 4   Ciudad Real 1
Coruña (A) 7   Ourense 4      

It is also interesting to note the percentage in which questionnaires have been used in the different languages.

  • Castellano 89,15%
  • Catalán 8,15%
  • Gallego 0,97%
  • Valenciano 0,84%
  • Euskera 0,34%
  • Arabic 0,20%
  • English 0,16%
  • French 0,10%
  • German 0,09%

Finally, it is relevant to note that the percentage of households that have used an electronic signature amounted to 29.90.