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Summary of coverage assessment and adjustment methodology

The main aim of this methodology was to estimate, and adjust the census data for the number of people and households not counted in the 2011 Census. A secondary objective was to identify and adjust for the number of people and households counted more than once, or counted in the wrong place, in the 2011 Census.

The Coverage Assessment and Adjustment methodology involved seven stages.

  1. ONS carried out a Census Coverage Survey (CCS), independent of the census. The survey was designed to establish the coverage of the census. The sample was drawn from each local authority.

  2. The CCS records were matched with those from the 2011 Census.

  3. The census database was searched for duplicates, and, together with the CCS, the results were used to estimate levels of overcount in the census.

  4. Populations of the sample areas were estimated from the results of the matching using dual system estimation techniques which enabled an estimate of those persons missed by both the census and the CCS to be made.

  5. Populations for each local authority by age and sex were then estimated using a combination of standard regression and small area estimation techniques.

  6. Households and individuals estimated to have been missed by the census were then imputed onto the 2011 Census database, with allowance for overcount. These adjustments were constrained to the local authority level estimates.

  7. All the census population estimates were quality assured using demographic analysis, survey data, qualitative information and administrative data to ensure the estimates were plausible.

Results of the coverage assessment, and adjustment methodology

Read about the outcome of the CCS, the coverage of the 2011 Census, the adjustments made to the statistics as a result of this methodology and quality information in the results of this methodology.


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