The 2001-2011 Temporal Output Area Classification (Temporal OAC or TOAC) is a geodemographic classification for the 2011 Output Areas in England.

A geodemographic classification provides a set of categorical summaries of the built and socio-economic characteristics of small geographic areas. Many such classifications are created entirely from data extracted from a single census of population. Such classifications can be considered to become less useful over time (e.g. later in the intervening period between decennial censuses) because of the changing composition of small geographic areas.

TOAC is a result of a project that utilises an innovative methodology that classifies both 2001 and 2011 census data inputs utilising a unified geography and set of attributes to create a classification that spans both census periods. Using this classification, it is possible to examine the temporal stability of the clusters and whether other secondary data sources and internal measures might usefully indicate local uncertainties in such a classification during an intercensal period.

Content

The data is available for download below, in Shapefile format. A data summary and variable dictionaries are also available.

Quality, Representation and Bias

A journal article accompanies TOAC which provides a thorough evaluation and methodological detail. All data used for this classification were sourced from the 2001 - 2011 Census so are bound by the usual operational quality / representation and bias of a national census. The geodemographic classification created presents a best effort of the authors to represent the characteristics of the population and geographic context over time, however, there are decisions made during the classification process that guide these representations. For a full overview of these decisions and their rationale, see the published paper.

Of particular note is the process used for the creation of the intercensal estimates for geodemographic clusters. These were created by drawing a linear path between the centroids of the 2001 and 2011 clusters, so therefore have different formulation to the 2001 and 2011 clusters.