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What is the Output Area Classification?

What is the Output Area classification – an introduction

The Output Area classification (OAC) distills key results from the 2001 Census for the whole of the UK at a fine grain to indicate the character of local areas. It was created in a collaboration between the Office for National Statistics (ONS) and the University of Leeds using the same well established methods as the related classifications of local authorities and wards. Like those it is freely available from ONS and other sources for all to use, and complements commercially available classifications. Among the wide ranging applications for OAC are the profiling profiling of populations, structuring other data, and the targeting of resources.

Help with Use

There has been no convenient source of guidance on area classification and geodemographics – the statistical concepts and interpretation, strengths and limitations, or about the main steps in application. There is also the question of choice between a classification which can be purchased in ready made packages or one like OAC which is in the public domain but usually requires more input from the user. The OAC User Group has been set up to provide help to those who use OAC or would like to use it, and to represent there interests. More on the User Group.

Area classification and geodemographics

Information can be found in print. A general introduction to geodemographics is provided by Peter Sleight in his chapter on ‘Geodemographic classifications and analysis’ in the Market Research Society ‘A guide to the 2001 Census’ (TSO, 2004), which also reviews the commercially available small area classifications. But this site now provides a simple introduction to geodemographics. Read more.

For more background on geodemographics – much of which is based on small area classifications – the Market Research Society Geodemographic Knowledge Base‘ is a rich source of links and contacts.

2001 Census based classifications and OAC

A first step in looking at the general concepts of areas classifications might be to visit the ONS website particularly to see how interactive maps show the telling patterns which emerged at the higher geographical levels, and are also a way of accessing further key information.

There are comprehensive introductions to OAC itself in a note or in an article by Dan Vickers and Phil Rees.This covers the creation of the classification, and the naming and visualisation of the clusters. It has UK maps of the seven ‘super groups’, together with a map showing the pattern of super groups in West Yorkshire, which illustrate the fine grain of the classification.

Output Area Geography

The 2001 Census Output Areas were specifically created for statistical purposes by an objective and automated method which delivered areas with populations quite tightly distributed around a population of 125 households. This reduced the effect of variation in population size on the classification, which may be an issue when classifying the variably sized populations of wards or when Census Enumeration Districts were used in the past. More information on 2001 Census geography and Output Areas, and to view maps of Output Areas.

Accessing OAC

OAC is available without charge from several sources.

OAC is a National Statistic and is Crown copyright, but supply is under very straightforward and unrestrictive terms and conditions.

The files of Output Area boundaries are available at minimal cost, but are supplied separately by ONS for England and Wales, by GROS for Scotland, and by NISRA for Northern Ireland. In effect the terms for use match those for OAC, but reselling the boundaries may require a licence.

Each source is somewhat geared to particular user communities, and, although the same classification is supplied by all, there are some differences in the supplementary material available. Supply in some cases is subject to registration for the service or is covered by a subscription for a more comprehensive package of data and software. More on data sources.

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  • The Output Area Classification

    The Output Area Classification (OAC) distills key results from the Census for the whole of the UK to indicate the character of local areas.

    It profiles populations, structures other data, and helps target resources. OAC is in the public domain, and the User Group supports and promotes its use as geodemography open to all.

    More about: OAC, Getting Started, the User Group.
  • Quick Links

  • Oac Interactive Map

    Extract from OAC Map
    OAC interactive map was developed by Richard Milton at the Centre for Advanced Spatial Analysis (CASA) at UCL.

    SOAC/DZ interactive map was developed by Maurizio Gibin and Alex Singleton also in CASA and the Department of Geography at UCL.