Consultation regarding the redraw of Data Zones

8. Census Output Areas

How we have produced draft 2011 Data Zones

8.1. In 2001, Census Output Areas (COAs) were used as the building blocks to produce Data Zone boundaries.

8.2. As COAs are used as building blocks for Data Zones, any changes to COAs will have knock on effects for Data Zones.

8.3. In the redraw process, 2011 Census Output Areas (COAs) were aggregated up to existing Data Zone boundaries on a best-fit basis to produce a first cut of updated Data Zones. Where the population of the Data Zone is outwith the accepted population range, that Data Zone has then been split into 2 or more Data Zones or merged with a neighbouring Data Zone in order to maintain roughly standard populations. These splits were made along Census Output Area boundaries and, where possible, any merges have been made within Intermediate Zone boundaries.

8.4. The new Data Zones will be called 2011 Data Zones, while the existing Data Zones would then be referred to as 2001 Data Zones.

8.5 Postcodes are allocated to Data Zones based on the location of the postcode centroid. This means that postcodes are essentially allocated to Data Zones on a best-fit basis. 2011 Census Output Areas respect postcode boundaries, so aligning Data Zone boundaries to 2011 Census Output Areas has the added benefit that Data Zone boundaries will also align to 2011 postcode boundaries.