Revising small area statistics geographies – data zones and intermediate zones: consultation

What are Data Zones and Intermediate Zones?

Data Zones and Intermediate Zones are small area geographies used in the production of official statistics. This section describes what Data Zones and Intermediate Zones are, and how they are used.

Data Zones

Data Zones are the key geography used for producing small area statistics in Scotland. They were first made available for use in 2004 following the publication of results from the 2001 Census and were produced to promote the production of local area statistics. They were revised in 2014, following the release of 2011 Census results.

Data Zones serve two key functions in the production of statistics. Firstly, they provide a standard, stable geography that can be used to publish statistics at a local level across a wide range of topics. They are designed to be large enough that statistics can be presented accurately without fear of disclosure or personal information. They are also designed to be small enough that they can be used to represent communities.

Secondly, Data Zones are used as a building block to construct statistics for higher geographies. Aggregations of Data Zones are often used to approximate larger areas of geography for statistics which might not otherwise be available. To support this, National Records of Scotland include Data Zones in their Scottish Postcode Directory, which provides a ‘lookup’ to higher geographies.

The use of Data Zones as statistical building blocks supports the implementation of the Government Statistical Service Geography Policy. For example, this policy states that statistics for all geographies should be built by first recording information at ‘building block’ level and then ‘best-fitting’ these building blocks to higher geographies, rather than recording or assigning information at a higher level directly. In Scotland, Data Zones, as well as Census Output Areas and Intermediate Zones, are the designated statistical building blocks under this policy.

Data Zones are built by combining Census Output Areas and were initially designed to satisfy a number of constraints. These are:

• Approximate equality of population, so that each Data Zone has a population of 500 to 1000 people.
• Compactness of shape.
• Approximate homogeneity of social composition.
• Existence, where possible, of some community of interest.
• Accordance with other boundaries of local significance.
• Accordance with prominent features in the physical environment.

In addition, Data Zones are designed so that they nest within Local authority boundaries. In practice it is impossible to satisfy all these criteria, so Data Zones must find a compromise between these criteria.

Intermediate Zones

Intermediate Zones are similar to Data Zones but cover a larger population and area. They are created by combining Data Zones to produce areas with a population of between 2,500 and 6,000. As for Data Zones, Intermediate Zones are designed so that they nest exactly into local authority boundaries.

Intermediate Zones are intended to be used to produce local area statistics where statistics cannot be published at Data Zone level due to the risk of disclosing sensitive information. The larger population of Intermediate Zones means that statistics are less likely to require disclosure control.