Super Output Areas

A set of slightly revised Super Output Areas (SOAs) were created for the 2011 census outputs. Details on what changes have been made are included in the NISRA Geography website

Super Output Areas (SOAs) are a new geography, which are being developed by NISRA to improve the reporting of small area statistics. SOA delineation work in Northern Ireland follows on from work already completed in Great Britain where, for England and Wales the Office for National Statistics (ONS) have created Super Output Areas (www.statistics.gov.uk/geography/soa.asp); and for Scotland the General Register Office for Scotland (GROS) have created Datazones (www.sns.gov.uk). 

Until now the standard unit of presenting local statistical information has been the Electoral Ward (Wards). However, in Northern Ireland, Wards vary greatly in population size (Census 2001), from fewer than 800 residents to more than 9,000. This is not ideal for regional and local comparisons.  Furthermore, standard output for the 2001 Census is available for a range of areas as defined on Census day - 29 April 2001. These areas are based on 5022 Census Output Areas (OAs), which have an average size of around 150 households. The OAs nest within the 582 Wards (1992) and the 26 Local Government Districts.  

The 5,022 Census Output Areas represent the smallest geographic units for which robust statistics could be produced while protecting the confidentiality of individual Census returns. They were designed to act as building bricks for the standard geographies described above and to enable statistical estimates for alternative geographies, such as areas defined as urban or rural, to be created. It is therefore reasonable to take account of OAs when building SOAs.

How the NI SOAs have been created. 

How the NI SOAs were created. 
SOAs have been created on a ward-by-ward basis taking into account measures of population size and mutual proximity. Initial work suggested that NI SOAs should have population counts that fall between a lower threshold of 1300 and an upper threshold of 2800, with a target size of circa 2000. Given that SOAs are constrained to Ward boundaries and using the suggested population parameters it followed that a significant number of individual wards formed a single SOA, as the populations fell within the accepted band. These accounted for more than 55% of all Wards. 

However, there were cases where the Ward population was either too large (> 2800) or too small (< 1300). In cases where the Ward population exceeded the upper threshold, the ward was split.  This was achieved by merging constituent Ward OAs, to create areas that had similar populations falling within the SOA population band. For example, if Ward A had a population count of 3400, it was prudent to create two SOAs for that ward, each with a population of circa 1700. Merging OAs, however, was dictated to a certain extent by proximity – an OA could only be merged with an adjoining OA. This decreased aggregation options as, in many instances, an OA (particularly one on the periphery of the ward) is adjoined by only one or two other OAs.  In general, the merging of OAs to create SOAs was driven by optimising the similarity of population size, taking account, as far as possible, of patterns of tenure and household type. 

On the other hand, Wards with population counts that fell below the lower population threshold were merged whole with a contiguous whole ward to create a SOA that satisfied the population banding. The main driver in these cases was proximity. 

Use of SOAs to report Deprivation Measures 

Deprivation Measures should be constructed at the smallest practicable spatial scale and that the ideal geography should possess similar sized populations. The smallest geography at which the 2001 Census was released was the Ward based Output Area. Despite their usefulness in identifying very small pockets of deprivation, for most domains of the proposed revised Measures, OAs would be too small to produce statistically robust information. However, it is possible to aggregate OAs into Super Output Areas (SOAs) - still constrained within ward boundaries - with a mean population of around 2000 people. These would have the advantage of allowing the identification of deprivation for smaller more evenly sized areas while maintaining statistical robustness. SOAs were used in the recent update of the English Indices of Deprivation and received general support.

Map images of the NI Super Output Areas, arranged by Local Government District can be viewed on NINIS website www.ninis2.nisra.gov.uk

Digital boundaries of the Super Output Areas can be downloaded below:

If you have a query on Super Output Areas:

Contact:
NISRA Geography
McAuley House
2 – 14 Castle Street
Belfast
BT1 1SA

Tel: 028 9034 8111
Email: ninis.nisra@dfpni.gov.uk