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Summary of the Census process

Planning and consultation

The Census is a complex undertaking and one that is only undertaken when it has been clearly shown that there is a need for it. Planning the Census is a long process, requiring many phases and it is vital that consultation takes place with a wide range of users of census data to determine their needs for data.

The content of the 2001 Census was formulated in consultation with users, through a structure of Advisory Committees and Working Groups, regulare communication via the Census News publication, information papers, the Internet and ad hoc public meetings. There were many full and detailed responses from users that were key in developing the final Census design.

Further information is available in the Consultating with users section.

Topic and question selection

Selecting the topics to be included in the 2001 Census, and finalising the format of the questions involved extensive consultation with users to identify the crucial information which was required from the 2001 Census. Special attention was given to the relationship between the information obtained rom each individual question included and the complex and detailed information that can be derived from combinations of questions. This is a particularly valuable aspect of the Census, where information on a range of topics is collected simultaneously, for the whole population, to form a single source from which important interrelationships between two or more topics can be analysed.

The process lasted five years and involved selection against criteria relating to user need, availability of alternative sources, quality, public acceptability and burden on respondents. The topics and questions included in the Census were those that were shown to provide information to be most needed by users and where, in each case, no other comparable and accessible source of the information was available in combination with other items in the Census.

Further information is available in the Consulting with users section and in the evaluation of the Data Needs project.  

Legislation

The 1920 Census Act allows for the carrying out of a census no less than five years after the previous census. However, various other legislative requirements need to be fulfilled before a census can be held. The first stage in the 2001 process was the publication of the 2001 Census of Population White Paper which set out the reasons for holding a census, the proposed questions, operational methodology and format of results. The White Paper was produced in March 1999, two years before the Census, to ensure sufficient time for public discussion of proposals.

Prior to every Census, a Census Order stating the date of the Census, the people who are required to complete the form, those who are to be included on the form and the topics on which questions will be asked is required to be approved by Parliament. The operational aspects of the Census also required Parliamentary approval and this information was set out in the Census Regulations, which contained details of how the Census was to be conducted and included a copy of the census form.

The decision to include a question on religion in the 2001 Census, resulted in additional legislation, which required amendments to be made to the 1920 Census Act, Census Order 2000 and Census Regulations 2000 to make provision for this new question to be asked.

Further information is available in the Census Legislation section. 

Census publicity campaign

A comprehensive publicity strategy was designed to ensure awareness of the Census throughout the population. The campaign aimed to influence positively those who might be resistant to taking part and, in so doing, promoting a prompt return of completed forms. It was also used to support the recruitment of Census staff.

Campaign activity promoted the key messages of confidentiality and social benefits, which had been shown by research to be the most important to the public. The key components of the publicity campaign included:

  • a successful advertising campaign, including the ‘Count Me In’ slogan and logo as part of a unified brand to convey the message of the Census and invoke the power of inclusion

  • using a coordinated approach to ensure that key public relations events were covered at both the national and regional level

  • the effective use of partnerships, most notably with BBC Local Radio and PR agencies

  • researching facts and figures in advance.

Further information is available in the report evaluating the publicity campaign

Fieldwork

The Census was designed to collect information on the resident population on Census Day - 29 April 2001. Before this day, enumerators were employed to deliver Census forms to every identified household space and communal establishment. Residents were asked to complete the forms with the information as correct on Census Day, and to post the completed forms back in a pre-addressed envelope. Where a form was not received through the post after a specified period, the enumerator visited the address in order to collect the form by hand. Special arrangements were made to enumerate the Armed Forces and people sleeping rough. The overall response rate (that is, the proportion of people included on a returned Census form) was estimated to be 94 per cent. Information on a further 4 per cent of the population was collected by enumerators.

Households absent from their usual address on Census day were required to complete a form on their return to that address (though many had done so beforehand). Where they did not, and in other instances where a household failed to return a form, the enumerator recorded the type of accommodation and an estimate of the number of rooms and number of residents. This information was used within the One Number Census process in adjusting the results for underenumeration in the Census.

Further information is available in the reports evaluating the data collection process. 

Census Coverage Survey

The Census was followed by the Census Coverage Survey (CCS), which took place between 24 May and 18 June 2001. This was an independent doorstep survey of a sample of a third of a million households, covering every local authority, which was used to adjust the Census counts for under-enumeration (see The One Number Census below). The Census Coverage Survey returned a household response rate (the proportion of identified households which were successfully interviewed) of 91 per cent.

Further information is available in the Census Coverage Survey section and in the report evaluating the CCS

Processing the data

Returned forms were fed through scanning machinery which captured all the ticked responses and stored written answers in digital form. The latter were coded into categories either by automatic systems that recognise terms given in response to questions, or by manual coding. This data then underwent an edit process to ensure that the data was consistent, and an imputation process to estimate responses for questions which had not been completed on the original form.

Further information is available in the report evaluating the census data processing operation. 

The One Number Census

A key strategic development for the 2001 Census was the adoption of the One Number Census process. This was used to adjust the results of the 2001 Census to take account of the fact that a single attempt at counting the population (the Census) never counts everyone.

The results of the Census were matched against those of the Census Coverage Survey. This enabled the numbers and characteristics of the total population to be estimated, including those not counted by either the Census or CCS. Data from administrative registers and demographic estimates were used to quality assure these estimates. All results from the 2001 Census thus incorporate allowances for Census underenumeration. Further information on the methodology of the One Number Census is available on the National Statistics website.

Detailed information about  the One Number Census process and methodology, including the research and consultation involved in the development, is available in the One Number Census section. 

Releasing results

The 2001 Census was the first in which a strategy for the development and release of results was agreed at the outset and included in the Census White Paper as Government policy. It was based on the simple premise that:

   “the investment of time and resources in a national census is only justified if the results are made accessible to users speedily and in a clear and usable form”

and that

   “technological developments should be harnessed in order to improve the accuracy, timeliness, accessibility and user-friendliness of published output”.

The work of the Output Project involved research, testing and implementation of new methods to create and supply statistical products using a wide range of formats. One of the key objectives of the project was to provide more of the results in electronic format, moving away from the largely paper based reports of the 1991 Census. Printed reports still played a part, but online channels such as Neigbourhood Statistics became a strategic tool for the releease of results, complimented by releases on CD and DVD. 

Further information is available in the About Census data section and in the reports evaluating Output policy and Output production.

Content from the Office for National Statistics.
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