1.1. Super Output Area and Output Area population estimates
Super Output Area (SOA) estimates are produced using a ratio change methodology. This method uses change in the population recorded in administrative sources as an indicator of change in the true population and is used to produce SOA estimates in intercensal periods. For consistency, lower layer Super Output Area (LSOA) mid-year population estimates are constrained to middle layer Super Output Area (MSOA) estimates, which in turn are constrained to local authority estimates.
LSOA population estimates are the starting point for calculating Output Area (OA) estimates. Administrative data sources are used to distribute the population, by single year of age and sex, between each OA within a single LSOA. Special populations (for example, prisoners and armed forces) are treated separately as they are static populations which that are not included in the administrative data sources used to calculate OA estimates.
Further detail on the production of these estimates is given in sections 4.1 and 4.2.
1.2. Health geography population estimates
Clinical commissioning group (CCG), NHS England (region, local office) and NHS England (region) population estimates are direct aggregations of LSOA estimates and therefore no detailed method is required for their production.
Further detail is given in section 4.3.
1.3. Ward and parliamentary constituency estimates
Ward and parliamentary constituency population estimates are based on aggregations of whole OA estimates. OA boundaries are not an exact fit (non-coterminous) for current ward or parliamentary constituency boundaries and are therefore allocated using a best-fit approach.
Further detail is given in section 4.4.
1.4. National Park estimates
National Park population estimates are provided for the exact boundaries of the National Park and therefore cannot be produced by aggregating whole OA estimates. The estimates are produced using a ratio change methodology that uses changes in the population of the wider area around the National Park (based on aggregations of OAs) as an indicator of the change in the true population of the National Park.
Further detail is given in section 4.5.Back to table of contents
The Office for National Statistics (ONS) produces estimates of the resident population of England and Wales. The most authoritative population estimates are produced every 10 years and are based on the results of the latest census. These are updated annually to produce mid-year population estimates in the intercensal period (referred to as “rolled forward” estimates). The population estimates give a stock count of people living in England, Wales, the regions of England and local authority areas, and the composition of the population in these areas by age and sex. Further population statistics, including migration estimates, vital events (covering births, deaths, marriages and divorces) and population projections are also available. Detailed results from the 2011 Census are also available and provide information on the characteristics of the usually resident population, for example, ethnicity and country of birth or marital status, for small areas.
Additionally, ONS produces population estimates for small areas within England and Wales:
Super Output Area (SOA) estimates – National Statistics including estimates for middle and lower layer SOAs (MSOAs and LSOAs)
estimates for other small areas – Experimental Statistics including wards, parliamentary constituencies, health geography1 and National Parks
Small area population estimates for mid-2001 to mid-2017 SOAs have been produced on 2011 Census boundaries. Mid-2002 to mid-2011 estimates for wards, parliamentary constituencies, health geographies and National Parks have been published on boundaries available when they were published following Census rebasing. The revised set of estimates for wards, parliamentary constituencies, health geographies and National Parks have been published on the boundaries in place as at June 2017. Geography information on OAs, SOAs, wards, parliamentary constituencies and CCGs can be found on our archive website.
Estimates have also been produced for mid-2001 to mid-2017 Output Areas (OAs) as these are the building blocks used to form estimates for wards and parliamentary constituencies.
Small area population estimates are produced using the best methods and data sources currently available. The 2011 Census has provided an opportunity to benchmark these estimates against census data and to analyse the level of accuracy that has been achieved. A report entitled Small Area Population Estimates (SAPE) Evaluation: Report on Accuracy Compared to Results of the 2011 Census compared “rolled forward” SOA estimates for mid-2011 (based on 2001 Census data) with 2011 census-based SOA estimates for mid-2011 and was published on 6 November 2015. This analysis will identify how well the ratio change methodology has performed in estimating small area populations over the intercensal period.
Notes for Overview of currently available estimates
- This includes clinical commissioning groups (CCGs NHS England (region, local office) and NHS England (region). Note estimates for former health geography areas (primary care organisations) are available for mid-2002 to mid-2012 but were discontinued from mid-2013 onwards, following a formal consultation procedure.
The population base from the 2011 Census underpins the mid-year population estimates base and is defined as follows:
“The 2011 Census was conducted on a resident basis. This means the statistics relate to where people usually live, as opposed to where they are on census night. Students and school children studying away from home are counted as resident at their term-time address. Wholly absent households were legally required to complete a census form on their return. No information is provided on people present but not usually resident.”
The definition of the population used in the small area estimates is consistent with that used for the published local authority mid-year estimates. These are broadly consistent with the definition used for the 2011 Census, although there are some minor differences in the treatment of armed forces.
In order to ensure that members of the armed forces were enumerated consistently, the 2011 Census was designed so that members of the armed forces were enumerated at their “permanent or family home” (this is considered to be their usual residence for census purposes). The mid-year estimates definition of usual residence for armed forces is different as it may be either their ”permanent or family home” or the armed forces base, depending on individual circumstances. For the purposes of calculating mid-year population estimates, an adjustment has been applied to the 2011 Census data at Output Area (OA )level to reallocate members of the home armed forces from their ”permanent or family home” to their place of residence at the armed forces base, where these are different.
The allocation of prisons differs from the 2011 Census allocation of prisons in a small number of areas. In the mid-year estimates at lower layer Super Output Area (LSOA) level prisoners are allocated to the LSOA in which the majority of the prison falls.
In practice, when producing a population estimate, a number of data sources have to be used, each with its own definition of usual residence. Further detail on the administrative datasets used to produce small area population estimates can be found in Appendix C.Back to table of contents
This section details the ratio change, Super Output Area (SOA), and best fit, Output Area (OA), methodologies used to produce small area population estimates in intercensal years. In a census year, population estimates are produced from census estimates and aged forward and adjusted to account for differences between census day and the mid-year (30 June) and usual residence definitions. Following a census, rolled-forward estimates for the intercensal years are revised to account for population change over this period and also to provide a consistent time series of population estimates. More details on the one-off methods used to produce estimates in census years and make the revisions to the estimates for the period mid-2002 to mid-2010 are included in Appendices A and B respectively.
4.1. Production of Super Output Area population estimates
The estimates for mid-2017 were produced using a ratio change methodology. Prior to the mid-2013 estimates, a number of different administrative datasets were used in the production of these estimates and these are documented in Appendix C. From mid-2013 onwards, only the patient register data was used.
The description of the methodology in the following sections uses the example of creating rolled-forward mid-2017 LSOA estimates. For example, the mid-2017 LSOA estimates were produced using mid-2015 LSOA estimates as the population base.
Middle layer SOA (MSOA) estimates are created in a similar manner using derived MSOA quinary age-by-sex change ratios and constrained to local authority mid-year estimates.
4.1.1. Step-by-step guide to methodology
The estimates were produced by applying the ratio change method to a LSOA estimate of the population base (the mid-2015 LSOA estimates) using patient register data. In previous years a combination of patient register and Child Benefit data was used. However, Child Benefit data could not be used from mid-2013 due to the impact of the government policy introduced in 2013 to restrict the availability of Child Benefit depending on family income. This issue is discussed in more detail in the Quality and Methodology Information document.
Before applying these change ratios some population counts are subtracted (referred to as the special population). These comprise UK armed forces, foreign armed forces and dependants, and prisoners. They are added again after these counts are constrained to the 2017 local authority mid-year estimates minus the special population.
The main assumption behind this ratio change method is that, for each area, the data should have a consistent relationship with the true population over time.
Change ratios were calculated by quinary age group and sex for the patient register data. The change ratios are calculated by dividing for each dataset the mid-2017 count by quinary age and sex with the mid-2015 count by quinary age and sex. For example, a mid-2017 count of 50 divided by a mid-2015 count of 40 gives a change ratio of 1.25.
For the original publication of mid-2013, and all subsequent releases, all age groups are covered by a single dataset (patient register); the LSOA change ratios for quinary age groups and sex in previous years are as follows:
- 0 to 4, 5 to 9 and 10 to 14 – child benefit data and patient registers
- 15 to 19 to 90 and over – patient registers
In summary, the ratios are then:
1. Applied to the mid-2016 LSOA population minus the mid-2016 special population by quinary age and sex.
2. Constrained to the mid-2017 MSOA estimates (less mid-2016 special population), which have been constrained to the local authority mid-2017 estimates less mid-2017 special population.
3. Then, mid-2017 LSOA estimates by single year of age and sex are produced by apportioning the quinary age counts to single year of age using mid-2017 local authority constrained patient register single year of age and sex counts.
4. These mid-2017 LSOA estimates by single year of age and sex are then constrained for consistency to mid-2017 MSOA estimates by single year of age and sex (these counts are derived from mid-2017 MSOA quinary age and sex estimates created using the same ratio change methodology as for LSOAs, apportioned to single year of age and sex using mid-2017 local authority constrained patient register counts by single year of age and sex).
5. Updated mid-2017 special population counts are then added back in to the quinary and single year of age and sex counts, to give mid-2017 LSOA estimates by quinary and single year of age and sex.
Where two change ratios were produced for some of the age groups to reflect the availability of two datasets for these age groups, the change ratios were averaged by adding together the two ratios and dividing by two.
Any change ratios produced for counts containing a zero by quinary age and sex were changed to 1 to ensure a valid ratio was produced. Where change ratios were applied to a base population by quinary age and sex of zero, the base population was changed to 1 to ensure an actual population count in the estimate, otherwise counts of zero in the base population would forever remain at zero.
Where SOA data for any of the datasets were identified to be erroneous, the calculated change ratios were updated to correct for identified errors. Criteria were developed to assist in the consideration of making any changes to the originally calculated change ratios.
An illustrative diagram of the ratio change method is shown in Appendix D.
4.2. Production of Output Area population estimates
Output Area (OA) estimates by age and sex are the building blocks used to form estimates for wards and parliamentary constituencies using a best fit method. OA estimates are consistent with estimates for higher geographies, such as SOAs, local authorities and the national total for England and Wales. The description of the methodology below uses the example of creating rolled forward mid-2016 OA estimates.
4.2.1. Step-by-step guide to methodology
Rolled-forward mid-2016 LSOAs are the starting point for calculating rolled forward mid-2017 OA estimates.
The following stages are followed to produce mid-2017 OA estimates:
1. Create mid-2016 LSOA estimates, by single year of age and sex
Rolled-forward mid-2017 LSOAs are the starting point for calculating mid-2017 OA estimates. These estimates are produced ahead of the other small area population estimates that are based on OA estimates.
2. Remove special populations
Special populations (prisoners and armed forces) are removed from the mid-2017 LSOA estimates. These populations are treated separately as they are static populations, at known locations, which are not included in the administrative data sources used to calculate OA estimates.
3. Apply patient register distribution
The distribution of population between each OA in a single LSOA can be determined from administrative data sources. The number of patients registered on GP lists in each OA at the mid-year point is used as a proxy for the true size of the population at the same point in time.
LSOA x, made up from five OAs x1,…, x5, has 20 males aged 0 and 15 females aged 0 at mid-2016.
The patient register distribution of 0-year-olds across the five OAs x1,…, x5 is shown in Table 1.
|OA||Males aged 0||Females aged 0|
Download this table.xls
The mid-2017 estimates for 0-year-olds in the five OAs are therefore given by the percentages shown in Table 1 multiplied by the mid-2017 estimate for the parent LSOA. The example results are shown in Table 2.
|OA||Males aged 0||Females aged 0|
|LSOA Total||%||OA Total||LSOA Total||%||OA Total|
Download this table.xls
4. Rounding and constraining
The resulting estimates for each OA by single year of age and sex are then rounded to ensure estimates of whole persons and constrained to the mid-2017 LSOA estimates by single year of age and sex. This process ensures that these estimates are fully consistent with mid-year population estimates for all higher geographies.
4.3. Production of health geography estimates
The Health and Social Care Act 2012 introduced a new structure for NHS organisation that replaced primary care organisations (PCOs) with clinical commissioning groups (CCGs) from 1 April 2013. CCG areas are formed from groups of LSOAs and therefore CCG population estimates are created by directly aggregating LSOA estimates.
CCGs are organised into the higher level of health geography of NHS England (region, local office) and NHS England (Region). These geographies are formed from groups of CCGs and therefore population estimates for these areas are also created by directly aggregating LSOA estimates.
In June 2018 there were 195 CCGs, 14 NHS England region local offices and 5 NHS England regions.
4.4. Production of ward and parliamentary constituency estimates
Mid-year OA estimates are directly aggregated to produce ward and parliamentary constituency estimates by single year of age and sex. This is achieved by using the published OA to ward and OA to parliamentary constituency geography lookups, which are available from the ONS Geography portal. Current estimates are published on 2014 ward boundaries and 2010 Westminster parliamentary constituency boundaries. These lookups allocate OAs to higher-level geographies using a best-fitting method. For each OA, a single fixed point is established that represents how the population is spatially distributed within the OA. These points are called population-weighted centroids and are calculated algorithmically based on 2011 Census estimates. The allocation of OAs to wards and parliamentary constituencies is based on where this point falls. Prior to 2011, ward and parliamentary constituency estimates were produced using a postcode best-fit method. Further details on this method are available under methods and guidance on our archive website.
In England and Wales there were 8,315 electoral wards as at 31 December 2017. Of these, 18 are sub-threshold wards that do not meet the minimum population requirements for data confidentiality (40 resident households and 100 resident people in the 2011 Census). As these are smaller than OAs they will not have separate OA estimates attached to them. In these cases, neighbouring wards have assumed the populations as detailed in Appendix E. More information on sub-threshold wards can be found in the best-fit policy document.
4.5. Production of National Park estimates
The ONS Geography policy states that statistics for higher-level geographies should be built from OA statistics using a “best fit” allocation. National Parks are an exception to this, as they cannot be suitably estimated through best-fitting of OAs. As such, estimates for National Parks for the 2011 Census were produced on an exact-fit basis; however, this process cannot be repeated for mid-year population estimates.
4.5.1 Estimates for mid-2011 onwards
The production method for National Park estimates is a two-stage process. The first stage rolls forward the estimates for a set of ad hoc age and sex groups1 (as per those used for the publication of 2011 Census data). The second stage rolls forward estimates by single year of age and sex and constrains these to the broader ad hoc age and sex group estimates produced in the first stage.
A ratio change method was used to roll forward the published 2011 Census National Park estimates (by the ad hoc age and sex groups) to produce mid-2011 estimates. This approach uses the population growth of the wider National Park area as a proxy for the change within the National Park boundary. These wider areas are the groups of OAs that have postcodes lying within National Park boundaries (for example, Figure 1), as determined by the National Statistics Postcode Lookup (NSPL, August 2013).
The same approach was then used to roll forward mid-2011 estimates to produce mid-2012 estimates (and to roll forward mid-2012 estimates to produce mid-2013 estimates).
Subsequent to the publication of mid-2011 and mid-2012 estimates, a method was devised to use more detailed 2011 Census data to produce estimates by sex and single year of age. This method included additional steps to ensure additivity to the published broader estimates. For consistency, this two-stage production process has been continued for mid-2013 to mid-2016, although only the single year of age and sex estimates have been published (as the broader estimates can be obtained by aggregating the single year of age and sex data).
4.5.2. Step-by-step guide to methodology
Stage 1 – Estimates for broader ad-hoc age groups
The following stages are followed to carry out the ratio change methodology to produce the National Park population estimates for each year. The example given is for producing mid-2011 rolled forward from 2011 Census, but the process is analogous for all years.
1. Create wider National Park areas from Output Areas (OAs)
The National Statistics Postcode Lookup (NSPL, August 2013) lists all current and previous postcodes and the higher geographies in which they are deemed to lie. This is used to create a lookup of OAs that fall wholly or partially within National Parks to form wider-National Park areas.
2. Calculate proportional change for rolling forward
Population estimates for these wider areas are created for 2011 Census and mid-2011 by aggregating the OA estimates for those periods. The aggregations are kept consistent with the 2011 Census National Park published estimates: persons; males; females; age group (0 to 4, 5 to 7, 8 to 9, 10 to 14, 15, 16 to 17, 18 to 19, 20 to 24, 25 to 29, 30 to 44, 45 to 59, 60 to 64, 65 to 74, 75 to 84, 85 to 89, 90 and over).
The proportional population change for each group is calculated for each area.
change (persons) = mid-2011(persons) / census (persons) change (males) = mid-2011(males) / census (males) change (18 to 19) = mid-2011(18 to 19) / census (18 to 19)
This change is then applied to the 2011 Census National Park estimates to produce unrounded unconstrained mid-2011 National Park estimates.
mid- 2011 National Park (persons) = 2011 Census National Park (persons) * change (persons)
The resulting estimates by sex and age group will not sum to the persons totals and therefore need constraining.
firstly, the persons data is rounded to the nearest integer
the estimates by sex are then constrained to persons totals
the estimates by age group are then constrained to persons totals
The unrounded sex and age group estimates are then rounded to the nearest integer and constrained to ensure consistency with the persons totals.
Stage 2 – Estimates by single year of age and sex
Due to the proximity of the 2011 Census to mid-2011, it was decided that the 2011 Census National Park estimates by sex and single year of age would not be rolled forward by ratio change, but would themselves be fitted to the mid-2011 published broader estimates using Iterative Proportional Fitting (IPF).
The unrounded estimates are then rounded to the nearest integer whilst maintaining previous totals.
Mid-2012 (and onwards)
1. Calculate proportional change for rolling forward
Population estimates for these wider areas are created for mid-2011 and mid-2012 by aggregating the OA estimates (by single year of age and sex) for those periods.
The proportional population change for each group is calculated for each area.
change (males aged 0) = mid -2012(males aged 0) / mid-2011(males aged 0)
This change is then applied to the mid-2011 National Park estimates to produce unrounded unconstrained mid-2012 National Park estimates.
mid - 2012 National Park (males aged 0) = mid - 2011 National Park (males aged 0) * change (males aged 0)
The resulting estimates by sex and age group do not sum exactly to the broader estimates and were fitted to these using Iterative Proportional Fitting (IPF)
The unrounded sex estimates are then rounded to the nearest integer whilst maintaining previous totals.
4.5.3 Mid-2016 estimates for Yorkshire Dales National Park and Lake District National Park
In August 2016 the boundaries of the Yorkshire Dales and Lake District National Parks were extended and the 2016 population estimates for these two areas reflect the population within the new boundaries.
As previously mentioned, National Park population estimates are provided for the exact boundaries of the National Park and therefore cannot be produced by aggregating whole OA estimates. Consequently it has been necessary to recalculate the population estimates for these two areas from the 2011 Census and roll these forward each year to 2016 using the methods outline in section 4.5.2.
The 2011 Census estimate for the National Parks was adjusted using published data from the 2011 Census at postcode level. A new lookup table showing which output areas intersect with the new National Park boundaries and form the “wider National Park area” was commissioned from ONS Geography.
4.6. Statistical disclosure control of estimates
The disclosure control processes applied to the estimates include small adjustments made to selected cells. Adjustments are made in such a way that inference of an underlying count is not possible but that the usefulness of the aggregated estimates is not materially affected.
Notes for Methods
- Total persons; total males; total females; and persons aged 0 to 4, 5 to 7, 8 to 9, 10 to 14, 15, 16 to 17, 18 to 19, 20 to 24, 25 to 29, 30 to 44, 45 to 59, 60 to 64, 65 to 74, 75 to 84, 85 to 89, 90 and over.
The estimates have been produced using administrative data sources to identify annual population change in intercensal years. Any deficiencies in these data sources may therefore impact upon the quality of the estimates produced. Where known deficiencies have been identified, corrective measures have been applied, though other deficiencies in the use of administrative data sources for producing population estimates may be less apparent, for example, list cleaning of the patient registers.
Small area population estimates were initially intended for publication by five-year age group and sex. More detailed estimates have since been provided by single year of age and sex. These are intended to enable and encourage further analysis and use of the estimates. Particular caution should be exercised in using estimates at a greater level of disaggregation – for example, for Output Areas (OAs), or for single year of age groups, as these would not be expected to have the same level of accuracy as the aggregated estimates.
5.1 Mid-2014 to mid-2017 estimates
In some local authorities the number of people included in patient register data in the current year has increased or decreased in a number of lower level Super Output Areas (LSOAs) and middle layer Super Output Areas (MSOAs) compared with the previous year’s data, which may be due to changes in administrative practices or may reflect genuine population change. The process of constraining LSOA and MSOA estimates to previously published local authority population estimates means that this pattern is not automatically reflected in the mid-year estimates.
5.2 Mid-2013 estimates
In some London local authorities the number of people included in patient register data in 2013 has decreased in a large number of LSOAs and MSOAs compared with 2012 data, which may be due to changes in administrative practices or may reflect genuine population change. The process of constraining LSOA and MSOA estimates to previously published local authority population estimates means that this pattern is not automatically reflected in the mid-year estimates. However, the constraining process has created some anomalous changes in a minority of LSOAs and MSOAs so some caution should be applied in interpreting estimates that show large percentage changes from mid-2012.
Small area population estimates for mid-2013 are affected by an error identified in the allocation of foreign armed forces in the mid-2013 local authority population estimates, an issue described in detail in the Quality and Methodology Information for those statistics. In total, the error affects population estimates for males and (to a lesser extent) females aged 18 to 59 in 45 local authority areas, particularly Forest Heath in Suffolk. As the small area population estimates are constrained to the local authority totals, these errors are carried forward into the figures for all small area geographies within (or containing) the affected areas. In the majority of areas the impact of the problem is negligible. However, some caution should be taken in interpreting figures for small areas known to have large numbers of foreign armed forces or located near foreign armed forces populations, particularly if these have changed significantly from the estimates for mid-2012.
5.3 Mid-2012 estimates
Mid-2012 small area population estimates rely on data from the patient register to provide the detailed information about the age and sex distribution of the population at OA level. By contrast, the mid-2011 OA estimates were heavily based on the results of the 2011 Census with minor adjustments to account for population change during the period between census day and the mid-year point. In a minority of areas, where the census distribution is significantly different from that given by 2012 patient register data, there may be large differences between the mid-2011 and mid-2012 estimates for some OAs. The OA estimates are constrained to the LSOA totals, so in general estimates for higher geographies, which often contain whole LSOAs, do not show as much variation as that seen at the OA level.
The mid-2012 population estimates use administrative data to account for the special population (prisoners and armed forces) that is present in each small area. The mid-2011 estimates included 2011 Census estimates of the special population, which in some areas may differ significantly from those given by the administrative data sources for mid-2012. These definitional differences may create unexpected changes in population between mid-2011 and mid-2012 for a minority of areas with large special populations. In a small number of areas, which have particularly large special populations, adjustments have been applied to the mid-2012 data to ensure population estimates remain plausible.
5.4 Mid-2011 estimates
For mid-2011 estimates based on the 2011 Census, no explicit adjustment was made for either internal or international in- or out-migration in the period from census day (27 March 2011) to 30 June 2011 (mid-year). However, an adjustment will have been made through the constraining to the local authority estimates that will have included these components. This therefore assumes that population change due to migration by age-sex (in- and out- migrants) in this period in all SOAs within a local authority is proportional to its size in those age-sex groups. This is unlikely to be true. However, as this estimate is for a short time, it is unlikely that the differences will be large.
5.5 Revised mid-2002 to mid-2010 estimates
Revised mid-2002 to mid-2010 estimates have been produced to provide a consistent time series of population estimates for the intercensal period. A method was put in place that reconciled the rolled forward LSOA estimates to the mid-2011 census-based LSOA estimates, balancing the need to produce a plausible revised backseries for total populations and sensible age-sex distributions that can be used as building blocks for producing best fit population estimates and bespoke population groups. The revisions also include a number of corrections for known issues with the previous series of estimates. The most important of these were:
an adjustment to correct for under estimation of Foreign Armed Forces (FAF) in Harrogate local authority in the mid-2009 to mid-2010 estimates
an adjustment to correct for boundary changes in Neath Port Talbot and Powys in mid-2005 to mid-2009
Research work undertaken prior to the publication of the revised mid-2002 to mid-2010 SAPE identified three possible methods to produce a backseries of population estimates. A “full assessment method” using census and administrative data along with an individual consideration of each area, where required, would have resulted in more accurate estimates overall. However, the advantages of increased accuracy were weighed against the impact on timeliness – that is, how soon the estimates could be published. Here there was a trade-off between different aspects of the quality of the estimates.
The “distribution of the difference” method provided the best balance in the majority of small areas between producing a plausible backseries of population estimates for each individual area and using a relatively straightforward method to allow timely publication. The method was designed to identify the difference between the census-based and rolled-forward mid-2011 estimates for each OA and LSOA and distribute this difference across the backseries in order to remove any ”jump” in the estimates between mid-2010 and mid-2011. As a consequence, the patterns of change identified in administrative data using the ratio change method may not be maintained in the revised mid-2002 to mid-2010 figures.
Limitations of this method are that it relies on making an assumption on how the difference between the two sets of estimates for mid-2011 has developed over time. This assumption will be particularly important for OAs or LSOAs where the 2011 census estimates were very different from the rolled-forward estimates.
As the difference is distributed across the OA and LSOA backseries by age-sex cohort, an implicit assumption is also made that populations in mid-2011 would have been in an area in 2002 at a younger age (that is, a 19-year-old male in mid-2011 would have been in the same area in 2002 but aged 10). This was a particular issue in LSOAs with high student-aged populations. Constraining the LSOA estimates to the revised subnational mid-year estimates will have corrected for this to a certain degree; however, a minority of LSOAs show very small counts at younger ages as a result of this assumption. Care must be taken in interpreting age distributions for areas affected by this issue.Back to table of contents
We are currently carrying out a quality review of SOA estimates. The review will assess the suitability of current methods used to produce these estimates. We will publish the main findings and recommendations.
For user feedback and further information, please contact the Population Estimates Unit:
Telephone: +44 (0) 1329 444661Back to table of contents
Contact details for this Methodology
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