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National reference metadata

Portugal

Reference metadata describe statistical concepts and methodologies used for the collection and generation of data. They provide information on data quality and, since they are strongly content-oriented, assist users in interpreting the data. Reference metadata, unlike structural metadata, can be decoupled from the data.

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Census 2011 round (cens_11r)

National Reference Metadata in Euro SDMX Metadata Structure (ESMS)

Compiling agency: Instituto Nacional de Estatística, IP

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25 February 2014

The EU programme for the 2011 population and housing censuses include data on persons, private households, family nuclei, conventional dwellings and living quarters

Persons enumerated in the 2011 census are those who were usually resident in the territory of the reporting country at the census reference date. Usual residence means the place where a person normally spends the daily period of rest, regardless of temporary absences for purposes of recreation, holidays, visits to friends and relatives, business, medical treatment or religious pilgrimage

Data are available at different levels of geographical detail: national, NUTS2, NUTS3 and local administrative units (LAU2)

21 March 2011

Counts of statistical units

Between the collection of the questionnaires and the dissemination of the results, the data from the 2011 Census were subject to a series of treatment processes that can be grouped into four stages.

1. Optical reading

Included the preparation of the questionnaires, involving verification and manual correction to the hierarchical and sequential ranking structure of the statistical units gathered on paper.

Digitalisation involved creation of images of the paper originals. The information was automatically recognised using ICR/OCR/OMR (Intelligent Character Recognition/Optical Character Recognition/Optical Mark Recognition) technologies.

2. Processing

During this stage the numerical characters that had not been recognised were processed and corrected and the validation rules defined for the fields containing such characters were checked.

The information gathered online was combined with the data from the paper questionnaires for further treatment.

During the validation of the hierarchy and numbering the hierarchy rules applicable to the questionnaires were validated.

During the intra-questionnaire validation and processing of alphabetical characters, the following were validated and corrected: the alphabetical characters in open questions; erroneous and duplicated markings; some validation rules. Problematic records were submitted to operators for manual correction.

During the sub-phase of validation and corrections of relationships any inconsistencies detected in the relationships between household members were addressed. During this sub-phase, the "Age" variable was also validated.

Expressions from open questions (countries, professions, etc.) were automatically coded using dictionaries and coding tables.  The system compared the expressions against those appearing in the dictionary; if the expression corresponded to the dictionary it was coded, if the expression was not recognised the record was returned to the operator for manual coding.

3. Automatic corrections

During the deterministic corrections sub-phase the consistency of the variables was assessed using a wide range of validation rules. Inconsistencies were addressed by means of deterministic corrections.

The "item non response imputation" sub-phase was intended to fill in gaps in the information by drawing on the rest of the information in the questionnaire or information from other questionnaires. Some variables were subject to deterministic imputation and others were imputed by Hot-deck.

4. Derived variables and specialisation

During this phase the derived variables resulting from the combination of information from one or more primary variables were calculated.

Data on population and housing censuses are disseminated every decade

All hypercubes (HC01 to HC60) were available by 26 November 2013.

There are no national practices which could impair the EU-wide comparability.