The One Number Census identified the extent of under-enumeration in the 2001 Census by conducting a large post-enumeration survey. The people identified as not counted were imputed to produce an adjusted total on which the final Census results were based. This met user needs for complete coverage, and reduced any bias in the results arising from differences between the characteristics of respondents and non-respondents.
Imputation of people
The numbers of people in each local authority, ward, Output Area, parish and postcode sector imputed into the final counts were used to produce an imputation rate. This rate was used to produce a set of quality indicators for each of these areas, together with quality indicators for each Strategic Health Authority, Primary Care Trust, and Health Board (Wales).
The quality indicator consists of a four-point scale based on the proportion of imputed people in an area.
Quality Indicator
Imputation Rate
1
Less than 5%
2
5% and less than 10%
3
10% and less than 20%
4
20% and over
Only residents in households were included in the calculation of the imputation rates, as no people were imputed into communal establishments by the One Number Census process. Students not at their term-time address were also excluded from calculations.
Another quality indicator is item response, measuring incomplete or inconsistent returns. Further information on Edit and Imputation can be seen HERE, and question non-response rates for each local authority are HERE.
There were also clusters of forms in 16 local authorities which were not processed for various reasons. A list of these local authorities affected, together with estimates of the numbers of people and households missed, is HERE.
The quality indicators for each local authority (including information on unprocessed forms), Strategic Health Authority, Unitary Authority (Wales), Health Board (Wales) and postcode sectors is available on spreadsheets through the links below. The spreadsheets for local authorities and Unitary Authorities also contain the quality indicators for wards, Output Areas, and parishes or communities (Wales).
Output Areas are small area building bricks for the release of 2001 Census results, and for use more widely in Neighbourhood Statistics. The vector (re-usable) boundaries for the 175,434 Output Areas in England and Wales are available without charge from Census Customer Services in two forms for users who wish to set up the boundaries in their own Geographical Information Systems. Further details can be found HERE.
Quality indicators for Parishes can also be accessed from the Local Authority spreadsheets.
The quality indicators for areas within each Strategic Health Authority in England and for each Health Board in Wales are also accessible below. Each Strategic Health Authority contains a number of Primary Care Trusts.
Browse for England and Wales Local Authorities, Health Authorities and Postcode Sectors:
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