5. Annex A Geo-referencing of DWP data
DWP data Geo-referencing
A large scale exercise has been carried out by Department for Work and Pensions to produce a single address for every individual at any point in time. This single address ( DWP) is based on the latest address that has been notified to the department in respect of any of the key benefits within WPLS.
Geographic referencing was carried out by the DWP using the ONS Official Neighbourhood Statistics ( NeSS) Address Matching and Reference Tool (Matchcode) and where applicable the relevant Post Code Directories as well. In accordance with NeSS Geography Policy each record was allocated to a fixed geographical area, namely Census Output Area and then all other higher geographies built up from this building block. Assigning a record to a 2001 Census Output Area ( COA) is done in a number of iterative stages:
Stage 1 - The NeSS Address Matching and Reference Tool (Matchcode) allocates an address to a COA, or the full 7-character postcodes (e.g. ZZ11 0ZZ) are matched against the geographic reference data to obtain a COA.
Stages 2, 3 and 4 - Where postcodes are partially completed, if the first 4, 5 or 6 characters of the postcode matched and were wholly contained within the same COA, then they were allocated to that COA.
Stages 5 and 6 - Remaining cases were allocated to Local Authority ( LA) to aim to get them in the right area and then randomly, but proportionally, assigned to a COA in that LA. Care is taken to exclude cases that are resident overseas as some benefits can be claimed by people who are now resident abroad. The COA counts were then aggregated up into caseloads at Data Zone levels.