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Super output areas (SOAs)

Background

Super output areas (SOAs) were designed to improve the reporting of small area statistics and are built up from groups of output areas (OAs).  Statistics for lower layer super output areas (LSOAs) and middle layer super output areas (MSOAs) were originally released in 2004 for England and Wales.  Scotland also released statistics for data zones (equivalent to LSOAs) in 2004 and intermediate geographies (equivalent to MSOAs) in 2005.  Northern Ireland introduced LSOAs in 2005 but do not have an MSOA geography.

2011 super output areas

Maintaining stability as far as possible was key for the 2011 Census.  LSOAs and MSOAs created following the 2001 Census continue to exist unless a significant population change occurred between 2001 and 2011, and household minimum and maximum thresholds were breached. Simplistically, where populations have become too big, the LSOA/MSOA has been split into two or more areas; where populations have become too small the LSOA/MSOA has been merged with an adjacent one.  Responses to the Output Geography Consultation from December 2009 to March 2010 were also considered in the redesign of OAs and SOAs. Consequently, the total changes across the output area hierarchy were no more than five per cent overall.

Population and household minimum and maximum thresholds for SOAs in England and Wales:

Geography Minimum population Maximum population Minimum number of households Maximum number of households
LSOAs 1,000 3,000 400 1,200
MSOAs 5,000 15,000 2,000 6,000

The total of 2011 LSOAs and MSOAs for England and Wales:

Geography England Wales
LSOAs 32,844 1,909
MSOAs 6,791 410

Data zones (DZs) and Intermediate zones (IZs) in Scotland will be reviewed following the 2011 Census and minor changes will be implemented, similar to those in England and Wales. 

This information will not be available until later in 2014.  For further information please see the National Records of Scotland (NRS) or the Scottish Neighbourhood Statistics website.  

SOAs in Northern Ireland have had minimal changes in three areas but the total number of SOAs has not changed since the 2011 Census.  Further details of Northern Ireland LSOAs can be found on the NISRA website.

Significant points of interest for the 2011 Census are that SOAs align to local authority district boundaries, including those that changed between 2003 and 2011, and also align at the border between Scotland and England.

Furthermore, the boundaries are available clipped to the coastline, for mapping, as well as to the extent of the realm, for geographic information systems and analysis. All SOAs have unique nine character codes, in line with all statistical geographies provided by ONS.

An upper layer super output area layer will not be created for England as part of the 2011 Census output area hierarchy.

Boundaries remain freely available under Open Government Licensing terms. 

2001 super output areas

The total of 2001 LSOAs and MSOAs for the UK:

Geography England Wales Scotland Northern Ireland
LSOAs 32,482 1,896 6,505* 890
MSOAs 6,781 413 1,235** n/a

* Data Zones
** Intermediate Geographies

2001 SOAs were initially introduced for use on the Neighbourhood Statistics (NeSS) website, but later became the standard units for presenting local statistical information across National Statistics.

Local statistics were produced at electoral ward/division level before OAs and SOAs were introduced.  This had drawbacks because electoral wards/divisions vary greatly in size, from fewer than 100 residents to more than 30,000.

This was not ideal for nationwide comparisons, and also meant that some data could not be released for smaller wards due to disclosure issues and the need to protect the confidentiality of individuals.

DZs and intermediate geographies (IGs) in Scotland are smaller in population size than their LSOA and MSOA counterparts in England and Wales.  DZs have a minimum population of 500 and IGs have a minimum population of 2,500.

In Northern Ireland, LSOAs have a population threshold of between 1,300 and 2,800.

Further information / Census geography products

ONS offers a range of 2011 Census geography products for England and Wales including:

  • Digital boundaries and centroids, for OAs and SOAs, which users can use in their own geographical information systems to carry out spatial analysis or web mapping.

  • Lookup tables showing OA aggregation to higher geographies, and comparison between 2001 and 2011 statistical geographies.

  • Reference (outline) pdf maps showing the areas used to present census statistics

For further information contact ONS Geography or visit the '2011 Census Geography Products for England and Wales' page.

For information regarding the census products for Scotland and Northern Ireland please refer to the relevant organisation.

SOAs: Frequently Asked Questions

For more information on SOAs, a set of frequently asked questions is available on the NeSS website.

 

Content from the Office for National Statistics.
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