§ Mr. Andrew Turner
To ask the Secretary of State for the Home Department what assessment he has made of the accuracy of the(a) 1981, (b) 1991 and (c) 2001 censuses. 
§ Ruth Kelly
I have been asked to reply.
The information requested falls within the responsibility of the National Statistician. I have asked him to reply.
Letter from Len Cook to Mr. Andrew Turner, dated 25 March 2003:As National Statistician and Registrar General for England and Wales I have been asked to reply to your recent question on what assessment has been made of the accuracy of the (a) 1981, (b) 1991 and (c) 2001 Censuses.A traditional component of every census is to undertake an assessment of the accuracy of the results. In previous censuses, particularly those in 1981 and 1991, part of this process was to undertake post-enumeration surveys to measure the extent of 149W coverage and question response that had been achieved. The detailed results of these assessments were published in a number of reports, and were summarised in the respective General Reports for these censuses, which were laid before Parliament under the provisions of section 4(1) of the Census Act.For the 2001 Census, the results have been subjected to a rigorous quality assurance process that followed an agreed strategy, which had been the subject of wide consultation with census users. Details of the procedures followed are set out in detail on the ONS website at www.statistics.gov.uk, and will also form the basis of a report to Parliament in due course. The usually resident population of each local authority by age and sex was considered in a consistent and detailed manner, involving comparison against diagnostic ranges derived from rolled-forward population estimates and aggregated data from administrative sources. We have assessed the consistency of each Local Authority's results with the information used for these comparisons. As well, an assessment of the quality of the diagnostic information itself is available. A series of evaluation reports on all aspects of the Census will be published this year.