The 2021 Classification of Output Areas (2021 OAC) is a hierarchical geodemographic classification which identifies neighbourhoods in England and Wales that share similar characteristics. The taxonomy classifies Output Areas into 8 different Supergroups, along with 21 nested Groups and 52 nested Subgroups.

The 2021 Census in Scotland was delayed until 2022, and resulting small-area statistics were released in late 2024. Release of Output Area statistics for Northern Ireland did not take place until after the deadline for creating the 2021 OAC, although summary 2021 statistics were available for less granular aggregations. Accordingly, a methodology was devised to create a UK wide taxonomy of OAs using modelled data for Scotland and Northern Ireland, with the intention of using this to frame available 2021 England and Wales data for timely release. The England and Wales classification could then be augmented when the data for Northern Ireland and Scotland became available. This methodology is detailed in Wyszomierski et al (2023). This enabled timely release of the 2021 England and Wales OAC as an Open data product by the ONS, and it is also available through the ESRC Geographic Data Service (GeoDS) here.

The modelled UK OAC cluster assignments for Northern Ireland and Scotland have now been updated using published 2021 and 2022 (respectively) Census data. This is called the ‘2021/2 UK OAC’. The update methodology is detailed alongside the slightly revised UK OAC pen portraits of the original taxonomy.

It is anticipated that the UK OAC will supersede the ONS and GeoDS England and Wales version of the classification. In the interim, UK-OAC will be available as a Safeguarded data product as a service to registered GeoDS users.

GeoDS also made the interim UK-OAC using modelled Northern Ireland and Scotland data available under its Safeguarded service. This remains available to research users who wish to carry out investigations involving comparison with past uses of this product (now called UK OAC-modelled). New users are advised to use this 2021/2 UK OAC.

Content

The data are supplied in CSV format. Additional information about these data, including the detailed typology, glossary of variables and terms, and distributional statistics, is available for download below, along with classification codes and labels.

Quality, Representation and Bias

Built using official government statistical estimates, the quality of the underpinning data is understood to be very high, and offers coverage of every UK neighbourhood. The classification methodology has been published and subjected to independent peer review. We provide additional documentation of the ways in which differences in Census variables differs amongst UK nations.

As the Census in Scotland was delayed from 2021 until 2022, and small area outputs from Northern Ireland's Census were not available at the time of production of the classification, the original classification contained some modelled estimates. A journal article provides a thorough description and evaluation of the approach. Now updated, UK OAC is constructed entirely from census data from 2021 in England, Wales and Northern Ireland; and 2022 Census data in Scotland.

UK OAC summarises general population characteristics and built environment attributes and are designed for wide use in research for policy. The Wyszomierski et al (2023) paper provides a full rationale and documentation of the work undertaken.