The Census Coverage Survey (CCS) was specifically designed to enable census population counts to be adjusted for under-enumeration at the national, local and small area level. It consisted of a completely independent and intensive face to face survey of a sample of over 16,000 postcodes containing 320,000 households drawn from all local authorities in England and Wales. The sample design took into account the uneven distribution of under-enumeration across the country by stratifying by a 'Hard to Count' index based upon characteristics likely to be associated with under-enumeration, such as the number of multi-occupied addresses.
The CCS was operationally independent from the census enumeration exercise. The CCS sample postcodes were kept confidential, CCS interviewers did not have any sight of the address lists produced in carrying out the census, nor the census forms returned in the area in which they were interviewing. The interviewers focused on making as many calls as necessary to achieve an interview, and the timing of these calls was varied to maximise the probability of making contact.
The CCS in England and Wales achieved a response from 91 per cent of the households identified by interviewers. This is a high response rate for such a large-scale voluntary survey when compared to other national surveys. The survey succeeded in meeting its objective of identifying households and persons that had been missed by the 2001 census.
Further information about the CCS is available through the links below or in the CCS Evaluation Report. CCS maps and hard to count information is provided for each local authority as part of the One Number Census Quality Assurance packs. Example packs are available using the related link above.
Information on the methodology used to promote independence of Census and the CCS results
Information on sample sizes in the Census Coverage Survey (CCS) for each local authority district in England and Wales.
Information on response rates achieved by the CCS for each local authority district in England and Wales