A best fit lookup between Output Areas (OA), wards and local authority districts (LAD) as at 31 December 2011 in England and Wales.
This lookup has been provided with a 'small population indicator' field. This field indicates those wards which have a very small population. There are two designated categories to describe the changes, - 0 - normal population, - 1 - very small population. Where a ward is smaller than an OA and therefore does not contain any OA population weighted centroids, the ward is allocated to the OA with its population weighted centroid nearest to any part of the ward. Information on the percentage of an OA’s population that falls into the higher geography has also been included in this best-fit lookup file. This ‘best-fit percentage' indicator has been calculated by working out the percentage of the OA’s population that falls exactly within the output geography. In the case of the OA to Ward lookup three OAs have a 0% of their population in the ward to which they are allocated. The affected OA are E00071944, E00120017 and E00026547, and all are the result of the wards not aligning with the 2001 OAs. The OAs with less than 100% of their population within their allocated ward are because of the process of 'best-fitting' by which they were allocated. Each OA was assigned to a single ward on the basis of its population weighted centroid. This meant that for statistical purposes, an OA had all of its counts assigned to that ward, even if the reality was that the geographic area may have covered several wards. This is why the 'percentage best-fit match' was created - the percentage of an OAs actual population that fell within its allocated ward rather than the total population of the OA that is used for statistical purposes. This was designed to help statistical users better understand the best-fitting process. (File Size 11.6MB).
Field Names – OA11CD, WD11CD, WD11NM, WD11NMW, SMPOPIND, PERCENTAGE_BF, LAD11CD, LAD11NM, LAD11NMW
Field Types – Text, Text, Text,
Text, Text, Text, Text, Text, Text
Field Lengths – 9, 9, 56, 56, 1, 3, 9, 36, 36
For more information and an overview of best-fitting follow this link -