Select Committee on Treasury Written Evidence

Supplementary memorandum from Mr Philip Redfern

  1.  This is in three parts. I) Support for the proposal of A R Thatcher (former Director of OPCS)[17] that the 2011 census should ask for information only about persons present on census night. That information would be the main element in estimating the resident population of each area. II) The need for a population register. III) Demographic checks on the census results. These last two topics are crucial to the future of population statistics, but the ONS Memorandum to the Committee has little or nothing to say on either of them.


  2.  As Thatcher points out in his Supplementary Memorandum, a form asking only about persons present on census night is simpler for the householder to complete. He does not have to consider who is usually resident at the address but is absent, nor does he have to give details of them. That will nudge up response rates. The fieldwork and processing tasks are reduced in scale and complexity, with significant reductions in cost. Tables of the usual residents in each area (down to postcode level) can be compiled by transferring a visitor back to the postcode of his usual residence.

  3.  Under the proposal the only residents of this country beyond census reach are those who are abroad on census night. This is an increasing number, probably about two million by 2011. An estimate of their numbers could be obtained from the International Passenger Survey by questioning residents returning to the UK in the days and weeks following census night. The present sample size would yield data on about 4,000 residents absent on census night, and give broad brush estimates by sex, age and area of residence. Whilst this may seem inadequate, it must be compared with the alternative ONS approach in which about one-third of the two millions absent abroad would not be picked up by census questions on absent residents.

  4.  The proposal to transfer data on a visitor to the postcode of his usual residence dispels the ONS criticism (Ev 216, #5.2.1) that data on migration, resident population and journey to work would be inaccurate. The casualty would be data on household composition which would omit absent residents; but, as noted above, about a third of absent residents would be missed by the ONS approach.

  5.  The proposal will eliminate the problem of distorted population geography inherent in ONS plans (see Ev 164, #21).

  6.  On balance, the simplicity of the Thatcher proposal—for the public, for enumerators and at all stages of processing—together with the cost saving more than counterbalance a marginal reduction in the quality of the household composition data.

  7.  A final point on the census form: the Evidence shows the pressure to add more questions, and ONS refer (Ev 217, 5.2.3) to their bid for funding for an extra page of questions per person. They will achieve that aim at the expense of poorer response rates and threats to the credibility of the basic census counts of the kind that so damaged the 2001 census. Fewer questions must be asked.


  8.  The Evidence shows widespread concern about migration figures based on small scale voluntary sample surveys and on disparate and disjointed administrative records, as well as doubt whether "tinkering" with existing migration sources will yield worthwhile results. There is also concern about the reliability of the 2001 census results. There is increasing recognition that the longer term solution is a population register that would coordinate the separate registers held by public agencies—particularly now that the administrative case for such a register has been accepted by the Government. Other countries provide examples of this new approach.

  9.  Ideas for a population register, leading ultimately to an Administrative Record Census to replace the conventional census, are outlined by the Statistics Commission (Ev 36, 20-22). The case is developed more fully by David Coleman (Ev 185-188) and myself (Ev 163, 8-11 and Ev 165, Section II).

  10.  In 2003 ONS published "Proposals for an Integrated Population Statistics System" which wrote (Section 5.5):

    "From 2013 onwards, the population statistics database would be updated regularly using information from administrative sources, the address register, the population register and surveys, creating a longitudinal database covering the whole population."

  11.  This ONS vision quickly evaporated. In 2005 an ONS-led project team (the Citizen Information Project) recommended that a population register should be created centred on the issue of ID cards, with a completion date (and therefore value to statistics) in the 2020s. This plan is now being implemented. The weaknesses of the plan are outlined in my Memorandum (Ev 165, 26-27) and are well known to ONS, but they are not mentioned in the thin ONS comment on this topic (Ev 220, Section 6.2). Moreover, ONS are not now playing a direct part in the development of a population register. If such a register is to provide proper information on migration before the 2020s, then it needs to be pursued with urgency and with a high-powered person in charge.


  12.  Demographic checks are standard practice in validating census results in any advanced country and may, as in the US 2000 census, lead to population estimates that depart from the census results. But the topic receives scant coverage in the Evidence. The Statistics Commission makes brief references to the check provided by the "roll-forward" from the preceding census (Ev 34, 4 and Ev 35, 13). Coleman (Ev 191-192) notes the low sex ratios in the 1991 and 2001 census results and discusses the demographic checks that ONS made in those years. But the lengthy ONS Memorandum is silent on this important methodology, on which validation of the census results depends.

  13.  Beginning with the paper I read to the Royal Statistical Society in 2003, I have on four occasions formally put to ONS a demographic check on the sex balance of the 2001 population estimates which finds a deficiency of half a million males in relation to females (HC 326-i, Ev 15, 32). Coleman devotes the final paragraph of his Section headed THE CENSUS (Ev 192) to a description of my check. However, ONS have not replied to any of my approaches nor made any reference to the sex ratio problem in their Memorandum. This is not an adequate response from a professional organisation. The validity of ONS's measure of the change in the sex ratio needs to tested and the underlying reasons for any change identified.

January 2008

17   Ev 39 Back

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