Neighbourhood Statistics Geography: England and Wales

Following the 2001 censuses, a new series of statistical reporting zones were developed for the publication of data derived from administrative sources. These data are primarily aggregated from individual records by government departments and then provided to the Neighbourhood Statistics Service.

Super Output Areas

The Neighbourhood Statistics Service uses as its building block the output areas (OAs) created for publication of the results of the 2001 census. However, very few new data sources have been added at this scale (an example is the counts of properties in each council tax band). A new set of areas known as "Lower Layer Super Output Areas" (LSOAs) with mean populations of 1,500 and a minimum threshold population of 1,000 was created by re-applying the computer algorithm that generated OAs from postcodes in the first place. The first data product to be released for these LSOAs was the Index of Deprivation 2004. The LSOAs thus contained aggregations of complete census OAs. They nested within their respective local authority district or unitary authority boundaries and respected 2003 standard tables ward boundaries. Each of these original LSOAs was a neat aggregation or split of wards or may be exactly the same as the wards in some areas. Unlike wards, whose population sizes vary widely, the LSOAs provide a consistently-sized statistical unit. A further level of aggregation was applied, this time involving local government consultation on the placement of boundaries, to create “Middle Layer Super Output Areas” (MSOAs) with a mean population of 7,500. The different levels have been used as containers for statistics which it is considered would be potentially disclosive if published for smaller areas. An originally-planned third tier, to be known as the “Upper Layer Super Output Areas” has never been produced.

LSOAs and MSOAs have not been given official names, although some local names are in circulation. They initially had codes which reflected the local government geography followed by a number for the MSOA and letter for LSOAs within each MSOA. 2001 census OAs were sequentially numbered within wards.

In preparation for the 2011 census, maintenance procedures have been applied to these geographical units, reflecting population change or decline, some requests from local authorities and some local authority boundary changes. The result is a slightly updated set of OA (2.6% change), LSOA (2.5% change) and MSOA (1.8% change) published in conjunction with 2011 census outputs.

In addition to these changes, the hierarchical coding scheme has been dropped and all zones in the hierarchy are now identified according to the Government Statistical Service (GSS) Coding and Naming Policy, which mandates 9-character codes of the type "E02000738". The new coding scheme is not hierarchical and can only be interpreted in so far as the first letter character indicates the country (here, E = England). The next two numeric characters indicate the area type (in this case 02 = MSOA) and the remaining six numeric characters are a unique identifier for the individual instance (i.e. this particular zone). These codes cannot be re-used if areas are redefined and a change history database (CHD) is being maintained by ONS to record the evolving structure.