Select Committee on Treasury Written Evidence

Memorandum from Worcestershire County Council


What are the uses of population estimates, and how far do current population estimates meet the needs associated with those uses? What are the effects of inaccuracies or inadequacies in such estimates?

  1.1  It is notable that small uncertainties which are marginal in National terms for total population are significant when applied in the context of different definitions (eg age, nationality), geographies and categories. The importance and the difficulties in capturing these "marginal uncertainties" should not be underestimated.

  1.2  Most particularly in recent years there is the impact of the most uncertain and volatile aspect of population estimation, migration. This is even more significant owing to public perception due to the visibility of "non-british" residents, and the impact of migrants demand on services being identifiable (eg owing to language).

  1.3  This has led (rightly) to an increased concern for some authorities of perceived inaccuracies in population estimation. Considerable work has been done by authorities individually, collectively, and by ONS, to address the concerns. It should be noted that, in our view, this has deflected effort from other developments in ONS's programme of modernisation and systems development.

  1.4  Of significance to us is the means of establishing a consistent source for population estimates data. Much of the information put forward in support of better population estimates cannot, for various reasons, be used consistently across the country (England, nor UK). We are satisfied that, within the resource limitations they have, ONS are pursuing the need for better data, it's proper analysis and use, with the right priorities. They have consulted their users on their programmes in this regard.

How appropriate is a definition of the population based on the usually resident population in the context of the needs of the users?

  1.5  The usually resident population definition is one amongst many population definitions of potential use to local authorities and the more complex living arrangements of modern life mean that ONS must adapt to the changing situation. At present students are allocated to their term time address for 100% of the time even though they spend part of their time at their parents' address, while increasingly people have several residences sometimes abroad. If you spend three days a week at one residence and four with your family at another having one simple view of usual residence is out dated. To this of course must be added the much discussed topic of migrants and in particular short term international migrants. Rather than just consider the single issue of short term international migrants it is important to consider all these issues together to reach a definition of the usually resident population.

  1.6   However we recognise the value in having a single standard definition which can be consistently applied across the country. Ideally, though, the population estimates system would provide enough flexibility to allow authorities to calculate populations against a range of definitions to better inform service provision, provide a relevant base for performance indicators and for policy development.

  1.7  ONS preparatory work for the 2011 Census has identified many ways of defining a person, in excess of 40, 23 alone for UK nationals, most of which are valid for some purpose. In practice LAs use different definitions; a population count could support these by providing different options.

  1.8  The range of alternatives would ideally include population present, day/night populations, term-time and holiday populations, weekday and weekend populations. This of course raises its own issue of the appropriate or incorrect use of any particular definition for any particular use. However, as mentioned below, the use of one definition does not prevent the misuse of the data.

  1.9  A major concern over population estimates is their use (along with population projections) in resource planning and allocation for Government departments, in particular, but not solely, CLG. Bearing in mind also the time delay in preparing population estimates, and still more, population projections, our view is that a more responsive solution for the concerns that LAs have in obtaining suitable resources could be to use other sources of data, particularly service-based data, for short-term resource planning. This would leave the estimates and projections to provide an "underlying, long-term" basis for resource decisions; these are typically reviewed for periods of 2-5+ years (1-2 years following), with projections having terms of 25 years and more.

  1.10  This is a matter of the fitness for use of (various) population counts.

  1.11  Notwithstanding the need for accurate population information, CLIP Population has identified areas where the use of population data is inappropriate in the light of its genesis, assumptions and robustness. Examples that we have identified include the following.

  1.12  Transport planning: A model used by the Department for Transport (DfT), called TEMPRO (for Trip End Model Presentation Program) has, in the past used as an input the trend-based ONS projection of population to derive households (an input to the model). This is increasingly being rectified by the use of "policy-based" projections, obtained through Regional Assemblies and (theoretically) aligned with Regional Spatial Strategies. There are still issues over currency, spatial disaggregation and the use of the modelling that are been addressed. An area of particular concern is the lack of data on the changing frequency of travel to work which has such a major impact on the results of the model. Estimating the proportion of the population who will travel four days or fewer to work each week is critical when calculating distance travelled for sustainability purposes or demand for travel.

  1.13  NHS resource and CLG Financial Settlement decisions use trend-based population projections that do not reflect a "likely" scenario. This

  1.14  All types of indicators increasingly use rates to illustrate year-on-year (or shorter period) change. In some cases these relate data from current administrative sources to out-dated, and "not fit for purpose" data. This is not to say the data are inaccurate, or the definitions unclear, but they are unsuitable for the purpose they are put to. (eg BV 17 uses as denominator a population that includes people not in work, when the numerator relates only to people in work.)

How does the quality and range of population statistics in England and Wales compare with that available in Scotland, Northern Ireland and internationally?

  1.15  We would note that population-related statistics in England and Wales compare very favourably with those in the other home countries, with, as far as we are aware, two exceptions. These are, in Scotland census and other data are not subject to disclosure provisions, and that there are housing-based data sources, derived from administrative data, that prove very valuable to verify population data on a consistent basis.

  1.16  While internationally there are official population statistics that are considered more robust and accurate, and command high levels of public trust, it is noteworthy that these are almost exclusively based upon a population register

  1.17  Thus, as the LGA submission states, it is sensible to monitor how these things are done elsewhere. ONS' intention to develop a business plan for an Integrated Population Statistics system, which would presumably examine approaches taken elsewhere, is therefore welcome.

  1.18  We note that there is ambivalence amongst local authorities on a register, but support for a more integrated, administrative data based system as proposed with the ONS Proposals for an Integrated Population Statistics System. This should deliver more robust statistics, but could not guarantee widespread acceptance. We also note that there is increasing public suspicion about collection of data on the individual, so a register system would at least have the advantage of being, in principal clear, transparent and in the open. It is important that a separation is clear between the administrative purposes of the register, and ONS's survey role.


How does the Census contribute to the creation of population statistics? Is the current frequency of Censuses appropriate and, if not, how frequent should Censuses be?

What lessons have been learnt from the Test Census carried out on 13 May 2007? What methods should be employed for the distribution and completion of Census forms, including the use of the Internet?

What steps should be taken to increase the rate of responses to the Census, particularly in hard-to-reach areas? How effective are plans to measure the extent of non-response to the 2011 Census?

To what extent is there a trade-off between the length of the Census form and its role in providing population information? What questions should be included in the 2011 Census?

What forms should the outputs of the 2011 Census take, how and when should they be made available and how should they be integrated and coordinated with other information on population?

  2.1  The importance of the Census in the creation of population statistics cannot be over-estimated; it is crucial. There are two aspects of the Census which need to be recognised, first that it is a key method of collecting local migration and travel to work data both of which have population definition implications but most importantly it is the only way that a complete understanding of the linkage between houses and population can be achieved. With a significant proportion of the population having several residences and vacant properties concentrated in particular areas it is important that double counting of the population does not take place. If issues such as gated communities, absent households, short term migrants and persons abroad are taken into account it is clear that we are dealing with a complex situation which requires either a census or a register which can identify if double counting is taking place. It is easy to criticise the Census but there are even greater problems with the alternative data sources.

  2.2  The only feasible alternative to obtaining even superficial information on the population (ie counts, age/sex, personal, not relationship information) at district level or below is a comprehensive, administrative register, and this would only provide part of the census statistics. Having said this, in terms of populations statistics, ie "simple counts", the currency and accuracy of information between censuses becomes increasingly important, such that currently, within 3 years of the release of census information, the dynamics of population change are problematic.

  2.3  We note that "hard-to-reach" groups often correlate to the "hard to deliver services" areas and rightly demand more attention, which is an approach of ONS census planning. However, evidence that a non-geographic, systematic deficiency in the census enumeration, applying to all areas (for example the lack of response for certain aged males), would require approaches that address being "hard-to-reach" across the whole Census geography. In other words, "hard-to-reach" areas are areas where certain "hard-to-reach" groups are concentrated.

  2.4  We would support the view that there is significant value of having 4 Census pages per person rather than 3. ONS have judged that response rates will not be affected, and the only deterrent is financial cost. We understand that this is the main difference between the 3 and 4 page versions. Less information would be gathered, in particular on educational qualifications and on industry/business of employer. These are both very important in getting an understanding of disadvantage.

  2.5  Output from the Census should be for the usually resident population but more flexibility is required to enable population counts on different bases to also be provided.


How accurate and useful are the mid-year population estimates for England and Wales, including information available for local authorities and Strategic Health Authorities?

How appropriate is the methodology by which mid-year population estimates are reached?

What are the most appropriate ways to ensure a common level of accuracy in mid-year population estimates for different areas and what steps should be taken to improve the accuracy in areas where population is hard to measure?

  3.1  The LGA submission generally covers this point and earlier paragraphs of this submission.

  3.2  With regard to the last question, the revision of statistics creates difficulties for local authorities because of the discontinuity and transition between significantly different totals. Most noticeably in recent times, this occurred following the 2001 Census, although this was not the first instance, and more recent revisions of estimates and projections have repeated the problem. A solution, but not one we would favour, is that the population estimates are shifted by only limited amounts towards the "new" totals.

  3.3  This is an intractable difficulty when thought of simply in terms of population estimates or statistics. It is the effects of the revisions that should be the focus of attention. We would particularly draw your attention to paragraph 1.8, with regard resource planning using consistent data across local authorities.


What role can and should be played by survey data in the compilation of population statistics?

What role can and should be played by data from General Practitioners and other health service data in the compilation of population statistics?

What other data sources can and should be used in the compilation of population statistics?

  4.1  It should always be borne in mind that the problems encountered by the Census, certainly when it comes to coverage, are experienced to an even greater extent by survey data. The particular strength of survey data relates to more complex questions where the presence of an interviewer is critical.

  4.2  Data taken from GPs registers provides particular challenges. There are often issues relating to the removal of patients from a list and this can lead to local biases. For example some surnames particularly amongst the ethnic populations are very common leading to difficulties in deleting records.

  4.3  We note that the work of ONS to develop an Integrated Population Statistics System would support many of the points made in the LGA submission about the benefits of administrative data. We also note, with reference to our earlier comments about the "marginal" factors, and the LGA's comments on "rare populations", that the collection of data on the scale and movement of migrants, especially international migrants, is the most critical element to be improved.


How effectively has the Office for National Statistics cooperated with stakeholders with an interest in and information relating to population statistics and how can cooperation be improved by the Statistics Board and by its Executive Office?

  5.1  We would especially support the points made in the LGA submission that ONS resources need to be taken seriously if the concerns are to be addressed, we have seen the effects of limitations in our work liaising with ONS, and have on several occasions expressed concern about work streams having to stop or be suspended.

  5.2   We would also reinforce the point that ONS needs cross departmental support in its efforts to improve population statistics. It is an area where co-operation in and thinking, planning and working will provide huge benefits. We gave our support to this approach presented to us by ONSCD at the last CLIP Population sub-group meeting.

December 2007

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