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Change since the census
Overview
ACORN is built using various sources of data for small areas or sometimes
individuals. This data includes Census demographics and lifestyle surveys amongst
other inputs. As a result it is completely redesigned every decade, following
publication of new Census data. However as the decade progresses Census
demographics get older and one wishes to ensure the classification is still the best
possible.
Unlike the redesign of Acorn each decade the update process leaves the overall
‘shape’ of ACORN unchanged. The 56 types, 17 groups and 5 categories remain, and
the names and descriptions have not changed. The change is in the people on the
ground – their ACORN code has been modified to reflect their changed
circumstances. We are seeking to identify and measure consumer changes since the
Census and, where appropriate, reclassify consumers accordingly.
There are two types of change, new developments and underlying change.
•
When new housing is built there is no past consumer data. The people
living in new housing do not (at that address) exist in consumer
databases, they have not filled in surveys and they were not measured by
the Census.
•
Underlying change in a postcode occurs as consumers move house, or as
they develop through their life stages. They might marry; have children,
change jobs and so on.
The process of updating ACORN considers both these types of change.
During the first update in 2005 some 125,000 postcode classifications were
improved. Of these 87,000 result in a change of ACORN group. A few thousand
postcodes, previously of a relatively middle or down-market nature have undergone
improvements resulting in their classification as ACORN group A: Wealthy
Executives.
Background
The two stage approach proved a very effective way of building ACORN. It also
provides the perfect framework for monitoring changes. As new data become
available the second stage can be repeated and the same process used to update the
ACORN code of postcodes where changes have occurred.
The second stage involves applying rules rather than traditional classification, which
means there are some key advantages to the approach. Firstly it is not necessary to
replicate every demographic input from the Census. Secondly one can consider
factors that were not available during the original development of ACORN.