Select Committee on Treasury Appendices to the Minutes of Evidence


Memorandum by The Market Research Society


  The Market Research Society (MRS) is the world's largest professional body for individuals employed in market research or with an interest in it. Founded in 1946, it is the largest body of its kind with over 8,000 members working in most organisations currently undertaking market research in the UK and overseas.

  The importance of the Census to market researchers is fundamental—much of their work, in terms of population surveys in this country, is underpinned by the Census.

  This submission has been prepared on behalf of the MRS by the Census and Geodemographics Group (CGG), which is an advisory group of the Society. The CGG represents the views and interests of census users in market research and CGG members are drawn from a wide range of sectors, including market research agencies, client users, users within census agencies and independent consultants who advise on census applications.

  The views expressed in this submission are supported by the Demographics User Group—which represents fourteen large commercial users of census and other government data—and the Association of Census Agencies—an informal grouping of census agencies.

  The main focus of this submission is the usability of outputs from the 2001 Census, however we will start with some general comments on innovations from a user's perspective, in order to "set the scene".


  When planning for 2001, ONS undertook to "break the mould" set by previous censuses. The 1991 Census had followed the model used in 1981 and had generally been successful. However, the 1991 results were called into question due to variations in the coverage rates for different demographic groups and so, for 2001, ONS made its goal to maximise population coverage and produce estimates which had been pre-adjusted for non response (the One Number Census).

  At the same time, ONS were able to take advantage of technological advances at key stages in its data capture and processing systems.

  As a result, a number of significant innovations were made in the 2001 Census:

2.1  Data Collection

    (a)  Geographic Information System (GIS) technology, combined with the Ordnance Survey AddressPoint product, was used to plan the enumeration districts and provide address lists to enumerators—this we welcome.

    (b)  The majority of forms were collected by post back from respondents; this was followed by enumerator visits in order to obtain forms from non-respondents. As census users, we were concerned about how well this procedure would work and the quality of the information that would be obtained. In previous censuses, the forms were personally collected by enumerators, who were thus able to check and rectify the form before leaving the household.

  In the event, the postal response was far greater than had been expected and, overall, ONS estimates that forms have been returned from some 98 per cent of households—which is similar to the coverage level in 1991. However, the data collection procedure has led to knock-on problems, such as the flood of calls to the Census Helpline and highly adverse publicity in the national press.

  In terms of quality of data collected, users will have to wait until the Census Quality Report is published in 2003. However, preliminary information on question non-response rates has just been published on the ONS web site. This shows that for the majority of questions asked in both 1991 and 2001, the non-response rate was higher in 2001—typically 1 to 5 per cent in 2001 compared with less than 1 per cent in 1991. For questions that were harder to answer (eg employment related topics) the non-response rate was typically 5 to10 per cent, with a highest rate of 10 to 15 per cent for professional qualifications and company size.

  Therefore the new data collection procedure appears to have had an adverse impact on question response rate, which we regret.

2.2  Processing

    (a)  We strongly welcome the move to 100 per cent coding of question responses; also the reorganisation of processing to publish outputs for tranches of statistics across all areas of the country, instead of on an area-by-area basis as done previously.

    (b)  The One Number Census should lead to improved outputs, but adds significantly to the processing time-scale.

    (c)  We currently expect to see results delivered to users in the first half of 2003, assuming that no major problems arise, and this is equivalent to the delivery time achieved on the 1991 Census (after the impact of a six month delay due to a data coding problem).

2.3  Outputs

    (a)  We also welcome the new geography of Output Areas which will be created for the 2001 Census, together with the associated package of geographical boundaries and mapping data to go with them.

    (b)  We appreciate the efforts put into consulting with users on the output products, however these have largely been negated over the last few weeks following the ONS announcement about new measures for disclosure control (see section 3 below).

    (c)  We welcome the agreement to include, at our request, Census Area Statistics for Approximate Social Grade (the ABC1 classification used in market research and advertising).

    (d)  We welcome, of course, the Census Access Project which will provide census results to users effectively free of charge. We expect that this, combined with availability of data over the Web, will significantly extend the user base and increase the uses made of the 2001 Census.


  The combination of output products and geography planned by ONS, in consultation with users, has been designed to obtain maximum benefit out of the 2001 Census, subject to confidentiality requirements. ONS have held four rounds of output consultations over the last three years and have made every effort to elicit the views of census users.

  However, this has all been placed at risk following the recent decision by the National Statistician over disclosure control, which was made public to users on 12 November 2001.

  The National Statistician has now decided to introduce additional disclosure control measures, which we are concerned could seriously degrade the quality and usefulness of Census results:

All counts in all Census outputs issued for England and Wales will be rounded either to zero or to numbers divisible by three.

  This rounding will apply to every cell count and every total in each output table, therefore the effects will be:

    —  The counts in each table will be either zero or multiples of three—this will be incomprehensible to ordinary users.

    —  If those counts are expressed as percentages, the percentage figures will "clump" on particular values and so will appear to be incorrect.

    —  The cell counts will not generally agree with the row and column totals, which in turn will not agree with the overall total, ie the table will be internally inconsistent.

  We believe that the rounding is unnecessary and will create confusion amongst inexperienced users and ridicule for ONS. It comes on top of perfectly adequate existing blurring measures built into the Census operation:

    1.  The swapping of records in the Census database, before producing outputs, which users had accepted as a method of blurring results while maintaining consistency between and within tables.

    2.  In addition, the database will already have been blurred as a result of the One Number Census processes and imputation modelling applied in order to fill gaps in the data.

    3.  The data will also be automatically blurred by the passage of time, since it will be two years out of date, when first results are made available to users.

  We understand that the Registrar General for Scotland has decided that the rounding measure is not necessary for the Census in Scotland (and that no decision has been taken as yet for Northern Ireland). Therefore why has this decision been taken for England and Wales, and why has it been made at this late stage without any user consultation?

  We are not alone in our belief that the National Statistician has made an uncharacteristically bad decision over disclosure control—we understand that he has received criticism from all major census users. As a result, he has arranged to meet and discuss the issue with representatives of the user groups on Thursday 13 December.

  Finally, as a further confidentiality measure, the National Statistician has decided to raise the population threshold for output tables to 100 resident persons and 40 resident households for the release of Census Area Statistics (CAS). We feel that these levels are unnecessary, as the Output Area production system has been designed to create areas containing 100-125 households. However, in rural areas such as many parts of Wales, the planned threshold is too high and would result in suppression of their CAS data.

  In 1991, the population threshold was 50 persons and 16 households. Prior to the recent decision by the National Statistician, the previous consultation paper by ONS had proposed a threshold of 50 persons and 20 households, which we feel would have been adequate.

10 December 2001

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