A Guide to the One Number Census (ONC)
The One Number Census (ONC) project aims to integrate the 2001 Census counts with the estimated level of underenumeration in the Census - that is the number of households and people not counted. First it will provide a new base for the mid-year population estimates at the Local Authority District (LAD) level, and second it will adjust the Census database itself for the estimated undercount so that all statistics sum to ‘One Number’ - the national estimate of the population.
What is a One Number Census?
Why is it necessary?
How will it be achieved?
The guide can be viewed HERE in Portable Document Format (pdf). For help in downloading pdf files click HERE.
Census 2001: Frequently Asked Questions
A Question and Answer document has been produced which provides answers to some of the frequently asked questions about the 2001 Census results. It contains information on the general accuracy of the Census, details of why the Census cannot be directly compared with a number of administrative sources, and information about enumeration of special groups such as students and prisoners. The document is available via the links below either in HTML or as a pdf file. For help in downloading pdf files click HERE.
Quality Assurance Methods
The One Number Census process results in a series of estimates of the population adjusted for underenumeration in the Census. A key part of the process is quality assurance. This will involve a series of quality checks, aided by data and grouped by age, sex and geography, drawn from a number of sources including demographic estimates and administrative records. In the event of any estimates being rejected at any stage of the process, a predetermined contingency strategy will be invoked.
The first document contained in this section gives a description of the quality assurance process and the contingency strategy proposed prior to the 2001 Census to quality assure the One Number Census (ONC) estimates.
ONS have now published two additional reports providing more detailed information. They are the 'One Number Census Methodology and Quality Assurance Process' report which describes the stages of the ONC process and provides a detailed description of the steps taken to quality assure the ONC estimates in 2001 and the 'Key Findings and Actions from the One Number Census Quality Assurance Process' report which describes the key findings and actions resulting from the ONC quality assurance process.
The White Paper
The GovernmentWhite Paper published on 4 March 1999 (ISBN 0-10-142532-5) announced the intention to carry out a Census Coverage Survey to assess the accuracy of the 2001 Census. The information gathered from this survey will be used in conjunction with the Census itself to produce a consistent set of counts from the 2001 Census that sum to the national estimate of the population on 29 April 2001. This is achieved through the One Number Census process.
Further Information on the One Number Census
Further information on the One Number Census, including Quality Assurance material at the Local Authority level, was published on the National Statistics Website on 23 December 2002. This has now been enhanced to add
The administrative data used in the Quality Assurance process (these are the comparator data used to calculate the diagnostic ranges found in the Local Authority charts)
Maps showing the location of postcodes sampled by the Census Coverage Survey
Please note that there is no risk of disclosure of personal information through release of these locations, as no information from the CCS will be published that could identify personal characteristics.
More details about the package are available HERE.
Additional information on the ONC is included in the information pages for local authorities that have been produced to help users understand the quality of the 2001 Census for each local authority. More details are available HERE.
ONC Steering Committee
The One Number Census (ONC) Steering Committee oversaw and guided the development of the methodology and management of the ONC project. Research papers were produced for each meeting of the group. These papers contained the detailed research undertaken throughout the project and the details of the final methodology.
Further details of the Steering Committee membership are available HERE.
The key Steering Committee papers (those papers that contain elements of the final methodology), are available HERE.
The remaining Steering Committee papers can be found below, grouped by year. Please note that there may be more than one paper on a particular subject, written at different stages of the development of the methodology under discussion. To access the papers, please click on the relevant year:
If you have queries about any of the information below, please email them to onc@ons.gov.uk
Royal Statistical Society meeting
A joint Social Statistics and Official Statistics RSS meeting on 31st October 2003 was convened to discuss the results of the 2001 Census, provide further information on the One Number Census process and give users an illustration of the Quality Assurance. The process of reviewing migration statistics was also presented.
Click HERE to view the powerpoint slides from the presentations.
The illustrative Quality Assurance pack is available HERE in Portable Document Format (PDF). For help in downloading pdf files click HERE.
One Number Census
