Origin / destination matrices

Statistics of flows of migrants or of journeys between residences and workplaces.

Presented as matrices (in computer files) of all areas by all areas at a particular geographical level. These give counts of either the numbers resident in one area one year before the Census but resident at the Census in another, that is the area to area 'flow' of migrants, or residents by address of workplace in the week before the Census, that is the area to area 'flow' of journeys to work. Further tables in the Census Area Statistics (CAS) and the Standard Tables give information on out migrants and in migrants in an area, and on workers at their address of residence and workplace.

Output Area

The smallest area for which detailed 2001 Census results are available. Output Areas (OAs) were created specifically for statistical purposes on the basis of data from the 2001 Census, using objective and systematic criteria in an automatic zoning process, and providing a consistent geographical building brick throughout England and Wales.

They have an average population size of 125 households and around 300 residents, each clustered around a single mode, always above the confidentiality thresholds of at least 100 residents and 40 households. They generally fit exactly within the boundaries of parishes/communities and wards as at the reference date of 31 December 2002, and comprise where possible of whole postcode units as at the time of the Census. The boundaries were created to enclose as compact an area as possible, although shapes may be attenuated by underlying patterns of settlement and postcodes. Where possible, OA boundaries were drawn to contain populations with homogenous characteristics, and around small, free-standing settlements.

Supply of digital boundaries for use in geographical information systems was a prime purpose of the OA production process, and these are available as files from Census Customer Services in MID/MIF or SHAPE formats generally without restriction on use.

Boundaries of OAs in local areas overlain on topographical base maps may be viewed in the 'Customised tables, charts and maps' option of Neighbourhood Statistics or in Nomis 'wizard' and 'advanced' queries as part of the 'geography' step after activating 'turn maps on'.

Super Output Area (SOA)

Two levels of larger standard building bricks built from OAs and providing a consistent geography for statistical output and stability over time.

Parish (England) / Community (Wales)

The most local level at which limited local government functions may be administered.

Parish/Civil Parish (England)

The parts of England that were administratively Rural Districts before local government reorganisation in 1974 are divided into parishes - sometimes known as 'civil parishes' to distinguish them from ecclesiastical parishes which may have different boundaries - often with boundaries dating back many centuries. The remaining parts of England may be termed unparished areas.

Parishes formed one or more Output Area (OA) where populations were above confidentiality thresholds. But a number fell below the thresholds, and were amalgamated with other parishes for the release of Census Area Statistics (CAS). Simple profiles are available for parishes with at least 40 residents and 20 households, and headcounts are available for parishes below those thresholds.

Community (Wales)

The administrative Rural Districts in Wales were divided into parishes prior to local government reorganisation in 1974, but parishes were then designated as communities, and the remaining parts of Wales were also divided into communities. They similarly formed one or more Output Areas (OAs), and the same measures apply for communities with sub threshold populations.

Boundaries of parishes and communities in local areas, overlain on topographical base maps may be viewed in the 'Customised tables, charts and maps' option of Neighbourhood Statistics.

Parliamentary Constituency (UK)

Area returning a Member of Parliament to the House of Commons at Westminster.

The number and boundaries of Parliamentary Constituencies are revised from time to time. At the time of the election of May 2005 there were 646 constituencies in the UK . The boundaries of those in England, Wales, and Northern Ireland had remained unchanged from the time of the Census in 2001, but new constituency boundaries were implemented in Scotland for the election. The boundaries for constituencies in Scotland in the UK Report for Parliamentary Constituencies are those existing at the time of the Census, and figures for the new constituencies are available the GROS website.

Postal geography / postal sector / postcode

A hierarchical coding system in the public domain which ultimately gives a unique identity to either single addresses or to small groups of addresses throughout the United Kingdom. Primarily developed and maintained by Royal Mail for the delivery of mail, but also an important means of coding other data on a common geographical basis and of defining areas to analyse and present such data.

A postcode has an outward code such as PO16, and an inward code such as PO16 7DZ. The whole code defines the address or group of addresses in a unit postcode (approximately 1.78 million in the UK in 2005). The units sharing an outward code and first digit of the inward code (PO16 7) form a postcode sector (11,597). The sectors sharing an outward code (PO1) form a postcode district (3,064), and the first part of the outward code (PO) is the postcode area (124). Postal geographies are not coterminous with any administrative areas.

All addresses in the 2001 Census were postcoded. The postcodes were used in the production of Output Areas, for the production of results for postal sectors, and for the production of look up files including postcodes.

Postal geography is revised from time to time by Royal Mail, and the postal geography used for Census output may have changed subsequently. The most up to date version available for statistical purposes is in the All Fields Postcode Directory.


A simple summary of 2001 Census results for quick reference and comparisons.

Content varies to suit the needs of the main users of profiles for:

  • UK Parliamentary Constituencies

  • postal sectors focused on commercial requirements

  • the Welsh language in Wales

  • parishes (England) /communities (Wales) specially designed to give simple figures for areas below the main confidentiality thresholds

Reference date

The date applying to the boundary of an area for which Census results are presented.

The boundaries of many areas for which Census results are presented change from time to time as a result of statutory reviews or administrative reorganisation, or for operational reasons. This is generally done for greater effectiveness or consistency in electoral representation, although the United kingdom is distinctive among the member states of the European Union for the large number of such changes. The electoral wards or divisions within each single or lower tier local authority are, for example, reviewed periodically.

Where not otherwise specified the boundaries of areas are as at Census day (29 April 2001), but the reference date of the boundaries of most administrative areas is 31 December 2002. These were the most up to date boundaries available before the main releases of results.


An account of the results of the Census laid before Parliament, and thus published, to meet the duty of the Registrar General under section 4.1 of the Census Act 1920 which governs census taking.

The act requires each report to be printed, although the number of printed 2001 Census volumes was much reduced compared with earlier censuses. The 2001 reports were succinct, and detailed results were included as supplementary CDs. Versions are also available without charge in downloadable form online, in most cases with supplementary information.

Although a report prefaces other releases of results, and the reports cover every topic in the Census and include all the main results, the bulk of Census results - particularly for local areas - is available via the web or CDs/DVDs.

Resolution (high / low)

Governs the precision and scale at which a digital boundary can be reproduced.

Digital boundaries stored at a high resolution have a high frequency of coordinates giving the precise position of the boundary and permit accurate reproduction at large scales. But such files are large, and, for less precise reproduction and to reduce file size, coordinates which have only a minor effect on position are filtered out to produce low resolution boundaries.

Rural area (2004 definition)

The Government definition and classification of the rural parts in England and Wales.

Each Output Area (OA) is classified on a 'morphological' basis - essentially indicating whether an area is built up or has more open land - which allows a larger area to be described in terms its of rural and non-rural parts, for example with Census figures for the two parts.

The main Census results on urban areas were prepared before the new classification was finalised, but, whilst all urban areas and settlements with fewer than 10,000 residents in 2001 are included in the rural category of the new definition, all results are compatible through the use of OAs as building bricks.


An area of urban land of 20 hectares or more with at least 100 residents but fewer than 1,500 - typically a medium sized village or very small town.

Areas of land with an urban use were recognised as part of the process of defining urban areas. Those with fewer than 1,500 residents in the 2001 Census - the minimum cut off point for an urban area - but at least 100 residents were designed as 'settlements', particularly so that figures would be available for named places such as villages which are only part of a larger administrative areas.

Shape format

A file format holding digitised boundaries for use in geographic software developed by ESRI.

Standard geographical hierarchy

Comprises of Output Areas (OAs) and all areas used to present 2001 Census results which are exactly coterminous with an OA or with an aggregate of two or more OAs.

OAs were created to be exactly coterminous with parish/community, ward, and local authority boundaries at a reference date of 31 December 2002.

Standard Tables

The standard set of comprehensive figures, with many detailed tables inter-relating characteristics, and available for a range of areas from local (ward) to the national level. They include all topics covered by the 2001 Census.

The Standard Tables comprise of

  • cross tabulations inter-relating two or more characteristics.

  • theme tables - cross tabulations relating various characteristics to standard categories for a particular group in the population
    A limited number of the univariate tables - counts giving a more detailed breakdown of a single characteristic - are included in the National report for England and Wales to supplement the Standard Tables and to complete comparability with the Census Area Statistics (CAS). Equivalents of all figures in the CAS may be found in the Standard Tables to facilitate comparison, although they may be broken down into more categories.

Statutory instrument

A legal measure which implements a specific secondary consequence of primary legislation, for example to implement new boundaries for local authorities.

Statutory instruments are part of United Kingdom law, separate from Acts of Parliament, which do not require full Parliamentary approval, and may either be passed by affirmative resolution of the Houses of Commons and Lords, or by negative procedure where they are simply laid before Parliament but subject to possible annulment, before they become law.

Generally, Census results are not released for areas with new statutory boundaries before a statutory instrument has become law.


SuperTABLE is the file format produced by SuperCROSS, the proprietary software supplied by STR (Space Time Research Ltd) and used to produce counts from the 2001 Census.

Most Census counts are available as SuperTABLE files. A free viewer is provided on Census CDs and DVDs, and can also be downloaded form the producer's website. An alternative is to obtain the counts from the Neighbourhood Statistics or Nomis websites.

Theme tables

Cross tabulations in the Census Area Statistics (CAS) and be Standard Tables relating various characteristics to standard categories for a particular group in the population.


Minimum population thresholds are applied for the release of sets of results to help prevent the inadvertent disclosure of personal Census information, and areas which fall below thresholds may be amalgamated with others to allow the release of results for the population of the amalgamated area.

The thresholds are:

  • Standard Tables 1,000 residents and 400 households

  • Census Area Statistics (CAS) / Key Statistics 100 residents and 40 households

  • parish/Community Profiles 50 residents and 20 households

There are no thresholds for headcounts, but small counts are adjusted as part of disclosure protection.

These measures are applied to predefined areas, such as parishes, wards or postal sectors, for which a particular set of results are generally available, but which may sometimes have populations below the thresholds. All Output Areas are above the threshold for Census Area Statistics (CAS) and Key Statistics.

Amalgamations are of contiguous areas, and of the same type of area wherever possible. They were done in consultation with the local authorities of the areas concerned. The few postal sectors which fell below thresholds were not amalgamated with other sectors as there was no definitive information about contiguity of sectors.

Unitary Authority

An authority providing a single tier of local government administration in parts of England outside Greater London and the metropolitan counties, and throughout Wales.

As part of local government reorganisation in England between 1995 and 1998, the two tier structure of counties and local authority districts was replaced in parts of England by 46 single tier Unitary Authorities, many of which are major urban centres outside the largest urban agglomerations.

Local government reorganisation in Wales in 1996 replaced the previous two tier structure entirely by 22 Unitary Authorities.

United Kingdom

The United Kingdom (UK) comprises England, Wales, Scotland, and Northern Ireland.

A Census 2001 report with figures for the UK Parliamentary Constituencies was made to the Westminster parliament, and results for the UK are supplied for use by the European Union. The 2001 Census based area classifications provide pictures of the UK as a whole, with downloadable UK summary datasets for local authorities, wards, and Output Areas

Otherwise 2001 Census reports were made separately under the separate Census legislation respectively for England and Wales, Scotland, and Northern Ireland. Although supplied separately by the three UK census organisations, there is a substantial common core of standard and comparable results in the Standard Tables and Census Area Statistics (CAS).

Univariate tables

Counts giving a more detailed breakdown of a single characteristic (variable), arranged as a table but without cross relation to other characteristics (variables).

Used in the Census Area Statistics (CAS) where detailed breakdowns in cross tabulations would have increased the risk of the inadvertent disclosure of personal Census information, but also included in part in the Standard Tables for comparability with the CAS where the breakdowns were not available in other tables.

Urban area

Major urban agglomerations, cities, and smaller towns defined in terms of their physical extent rather than by any administrative boundaries.

Census reports with results for urban areas and the remaining 'rural' populations were first produced from the 1981 Census to meet a widespread interests in towns and cities as such when the administrative distinction between urban and rural areas disappeared after local government reorganisation in 1974. Similar reports have been produced from the 1991 and 2001 Censuses.

The method of defining an urban area has remained generally consistent for the 1981 - 2001 Census reports - the Office of the Deputy Prime Minister and its predecessors have identified area of urban land use (a tangible 'bricks and mortar' approach) in England and Wales of at least 20 hectares in extent, and then the smallest 'building bricks' for which Census results have been produced - Enumeration Districts in 1981 and 1991, and Output Areas in 2001 - have been fitted to the boundaries of the urban land, and, where the Census day population exceeds a minimum size (1,500 residents in 2001), the area of land was designated as a named urban area, with sub-divisions where appropriate. Results are also available from the 2001 Census for settlements with less than 1,500 residents. The reports contain more details of the process, and have maps of the urban areas.

The reports do not contain a definition of rural areas or a rural population as such, and although the ten percent of the population remaining outside the urban areas may be regarded as 'rural', small towns may be considered to be part of a broader definition rural population, and the Government issued a new definition of rural and urban areas in 2004, for which 2001 Census results are available, and which places some 19 per cent of the population of England and Wales in rural areas.

Urban subdivisions

Major urban areas and others with more than one central focus are divided where possible to produce figures about localities within them. Previously separate urban areas, where urban land has merged, are also recognised by subdivisions where possible. Subdivisions often follow the boundaries of local authorities existing before reorganisation in 1974, or the boundaries of current authorities within urban areas.