Kent Output Areas and Super Output Areas
Output Areas and Super output areas
Super Output Areas (SOAs) are a geography
designed by The Office for National Statistics (ONS) for the
collection and publication of small area statistics.
Until the creation of SOAs, the standard unit
for presenting local statistical information has been the electoral
ward/division. This has two disadvantages:
- Electoral wards/divisions vary greatly in size, from fewer than
100 residents to more than 30,000. This is not ideal for nationwide
comparisons, and also means that data, which can safely be released
for larger wards, may not be released for smaller wards due to
disclosure requirements (i.e. the need to protect the
confidentiality of individuals).
- Electoral wards/divisions are subject to regular boundary
changes. This creates problems when trying to compare datasets from
different time periods.
The ONS therefore developed a range of
statistical geographies that would be of consistent size and whose
boundaries would not change. These would be built from groups of
Output Areas (OAs) and would be known as Super Output
Output Areas - OAs are the smallest level of
geography for the release of Census data and have a minimum
population of100 people or a minimum of 40 households.
Lower Super Output Areas - LSOAs have a
minimum population of 1000 and are built from groups of OAs and
constrained by the ward boundaries used for Census outputs.
Middle Super Output Areas - MSOAs have a
minimum population of 5000 and are built from groups of LSOAs and
constrained by the local authority boundaries used for Census
In theory, SOAs are better for statistical
comparison as they are of a much more consistent size and each
layer has a specified minimum population to avoid the risk of data
disclosure (releasing data that could be traced to
individuals). A key principle of SOAs is that they will
not be subject to frequent boundary changes. However, in light of
the 2011 Census population results some OA, LSOA and MSOA
boundaries were re drawn. Changes in population meant that
some of these small area geographies fell below the minimum
population thresholds whilst others grew and became higher than the
minimum requirement of the next level. As a result some OAs
and SOAs were either merged or split to create new areas which
comply with the required population thresholds that prevent any
Unfortunately the changes in the small area geographies mean
that for certain individual SOAs any comparison of time series data
will be difficult . To help identify these changes we have created
maps for both LSOAs and MSOAs.
More information on SOAs is available from the Office National