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Statistical bulletin: Super Output Area Mid-Year Population Estimates, Mid-2011 (Census Based) This product is designated as National Statistics

Released: 11 April 2013 Download PDF

Key points

  • In mid-2011 there were 34,753 lower layer Super Output Areas (LSOAs) in England and Wales with a mean population of 1,620 and 7,102 middle layer Super Output Areas (MSOAs) with a mean population of 7,800.
  • The LSOAs with the highest population densities are all in Inner London, with the most densely populated area being Kensington and Chelsea 021C.
  • The least densely populated LSOA in England and Wales is Northumberland 019C in Northumberland National Park.
  • Mid-2011 Super Output Area (SOA) population estimates are based on the results of the 2011 Census. Previous estimates based on the 2001 Census and updated annually over the ten year period were within 5% of the 2011 Census based estimate in approximately 65% of LSOAs.
  • SOA population estimates are particularly important for use in many areas of research as they provide key demographic information on small geographic areas that were designed specifically for the purpose of enabling statistical analysis.

Summary

This bulletin presents the 2011 mid-year population estimates for lower layer and middle layer Super Output Areas (LSOA and MSOA respectively), which are small areas within England and Wales. These estimates are based on the results of the 2011 Census and are available for the new LSOA and MSOA geographic boundaries published in October 2012.

Population estimates for LSOAs and MSOAs are often used for research and analysis as, unlike other small area geographies such as wards, they are specifically designed for statistical purposes. In particular, they are used by both central government departments and local authorities for a range of purposes including planning and monitoring of services and as denominators for the calculation of various rates and indicators.

 

Introduction

Mid-year population estimates for 2011 for England and Wales, regions within England and local authorities within England and Wales, based on the results of the 2011 Census, were published on 25 September 2012. The estimates refer to the usually resident population as at 30 June of the reference year and are published annually. In mid-2011 the population of England and Wales was 56,170,900, an increase of 7.3% over the ten years since mid-2001.

Small Area Population Estimates

Mid-year population estimates for small areas within England and Wales are also published annually, usually approximately three months after the publication of national, regional and local authority level estimates. However, these estimates for mid-2011 have been published approximately six months after the national estimates due to the additional time required to incorporate the results of the 2011 Census.

The mid-2011 small area population estimates, referred to in this bulletin, are based on the 2011 Census, updated to account for population change during the period between Census day (27 March 2011) and the mid-year point (30 June 2011). A combination of registration, survey and administrative data is used to estimate the different components of population change at both small area and local authority level. A full description of the methods used to calculate mid-2011 small area population estimates is available in the methodology guide (130.7 Kb Pdf)  published on the ONS website.

The mid-2011 small area population estimates are fully consistent with population estimates for higher levels of geography including local authorities, regions and the national total for England and Wales. The back series of small area population estimates for mid-2002 to mid-2010 will be revised later in 2013 to be consistent with the revised population estimates for England and Wales, published in December 2012, and the revised population estimates for local authorities, due to be published on 30 April 2013.

Small Area Population Estimates are used by both central government departments and local authorities for a range of purposes including planning and monitoring of services and as denominators for the calculation of various rates and indicators. For further information on the quality and use of these statistics, please see the Quality and Methodology Information for Small Area Population Estimates.

What are Super Output Areas?

Super output areas (SOAs) were introduced in 2004 to improve the reporting of small area statistics. They are built from groups of Census output areas, are of a consistent size and are not subject to boundary changes between censuses. The comparability and stability of the geography is a key benefit to users of statistics which cannot be provided by other small area administrative geographies such as wards or parishes.

Following the 2011 Census, some boundary changes to SOAs were required and a new set of SOA boundaries was published in October 2012. However, the stability of the geography has been largely maintained with 97.5% of lower layer SOAs and 97.9% of middle layer SOAs remaining unchanged. For further information please see the full report: ‘ Changes to Output Areas and Super Output Areas in England and Wales, 2001 to 2011 (287.3 Kb Pdf) ’.

The mid-2011 population estimates presented in this release are provided for these new boundaries.

Two levels of SOAs are available in England and Wales:

  • Lower layer (LSOAs) designed to have a population of between 1,000 and 3,000 in 2011. There are 34,753 LSOAs in England and Wales.

  • Middle layer (MSOAs) designed to have a population of between 5,000 and 15,000 in 2011. There are 7,201 MSOAs in England and Wales. MSOAs are aggregations of LSOAs.

Further information on SOAs can be obtained from the geography section of the ONS website.

 

 

Mid-2011 Super Output Area Population Estimates

At mid-2011, the mean population of lower layer Super Output Areas (LSOAs) in England and Wales was 1,620, with population sizes ranging from 990 in City of London 001E to 8,160 in Oxford 008A – an area including many Oxford University colleges. Figure 1 below presents the overall population size distribution of LSOAs in mid-2011, which shows that over 80% of LSOAs have a population of fewer than 1,800 usual residents.

Figure 1: Distribution of LSOAs by total population estimate, mid-2011

Figure 1: Distribution of LSOAs by total population estimate, mid-2011
Source: Office for National Statistics

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The mean population of middle layer Super Output Areas (MSOAs) was 7,800 in mid-2011. Excluding the Isles of Scilly, the smallest MSOAs had a population of 5,000 whilst the MSOA with the largest population at mid-2011 was Richmondshire 004 with approximately 16,400 usual residents. This area has a high population of armed forces including those stationed at Catterick Garrison. The overall population size distribution of MSOAs in mid-2011 is shown in figure 2 below.

Figure 2: Distribution of MSOAs by total population size, mid-2011

Figure 2: Distribution of MSOAs by total population size, mid-2011
Source: Office for National Statistics

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Age Distribution

The median age of the population of England and Wales in mid-2011 was 39.5, an increase of 1.6 years since mid-2001.

The median age for LSOAs within England and Wales varies widely between different areas. In mid-2011 the lowest median age in an LSOA was 18.3 in Horsham 008E, an area in West Sussex containing a large boarding school. Eight of the top ten areas contain boarding schools, whilst one includes halls of residence for the University of Sheffield.

Table 1: LSOAs with youngest median age, mid-2011

Rank LSOA Median Age
1 Horsham 008E 18.3
2 Rutland 005D 18.5
3 Bracknell Forest 012D 18.5
4 Harrow 029D 18.7
5 Salford 016E 18.7
6 West Berkshire 011C 18.8
7 East Northamptonshire 002E 19.0
8 Mendip 012D 19.6
9 Sheffield 038C 19.8
10 South Norfolk 004D 19.9

Table source: Office for National Statistics

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The highest median age in mid-2011 was 71.5 in Eastbourne 012B. Eight of the top ten LSOAs with the highest median ages, as shown in table 2 below, are located in coastal areas of southern England which are known for their large populations of people of retirement age. The exceptions are Wealden 018A which is a rural area located close to the South Downs National Park and King’s Lynn and West Norfolk 017D which is located in the town of Downham Market.

Table 2: LSOAs with oldest median age, mid-2011

Rank LSOA Median Age
1 Eastbourne 012B 71.5
2 Poole 018B 70.7
3 Christchurch 003A 70.0
4 King's Lynn and West Norfolk 017D  69.2
5 Christchurch 003B 68.9
6 East Devon 012B 68.6
7 East Devon 020B 67.7
8 Wealden 018A 67.2
9 Rother 008B 66.7
10 East Devon 017A 66.7

Table source: Office for National Statistics

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Overall, the majority of LSOAs (85%) have a median age between 30 and 50. Figure 3 below shows the distribution of median age by selected five year age bands.

Figure 3: Distribution of LSOAs by median age, mid-2011

Figure 3: Distribution of LSOAs by median age, mid-2011
Source: Office for National Statistics

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Population Density

LSOAs are designed to have similar levels of population. Population density, that is the number of people living per square kilometre, can be used to highlight how different LSOAs are in terms of the geographic size of population settlements they include.

In mid-2011, the population density of England and Wales was 372 persons per square kilometre. Approximately 85% of LSOAs had a population density higher than that of England and Wales as a whole. Population density was less than 5,000 persons per square kilometre in approximately 69% of LSOAs and approximately 8% had a population density of 10,000 or more persons per square kilometre.

Table 3: LSOAs with highest population density, mid-2011

Rank LSOA Population Density (persons per sq. km)
1 Kensington and Chelsea 021C                68,400
2 Islington 011F                50,600
3 Tower Hamlets 032D                47,100
4 Westminster 024E                46,400
5 Westminster 022D                43,800
6 Tower Hamlets 025C                40,100
7 Westminster 014F                39,400
8 Westminster 017A                39,100
9 Hammersmith and Fulham 023E                38,600
10 Hammersmith and Fulham 015B                38,000

Table source: Office for National Statistics

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The top ten LSOAs with the highest levels of population density are all in London. The LSOA with the highest population density in mid-2011 was Kensington and Chelsea 021C. This is an area where, approximately, 1,300 people live in 0.02 square kilometres, resulting in a density of 68,400 persons per square kilometre.

Map 1 below shows the population density of LSOAs within London for mid-2011. Areas with the highest levels of population density are generally concentrated in Inner London local authorities north of the River Thames, as shown in table 3 above. However, there are also areas of high population density in local authorities south of the river such as Southwark and Lambeth.

Additionally, the map shows those areas of Inner London local authorities which have relatively lower population densities (between approximately 500 and 2,500 persons per square kilometre), such as the LSOAs in Westminster which include Hyde Park, Kensington Gardens, St James’s Park and the land surrounding Buckingham Palace.  The course of the River Lea through North London can also be seen due to the areas with low population density extending from Enfield in the north to the River Thames near the Isle of Dogs.

Map 1: Population density of LSOAs in London, mid-2011

Map showing the population density of the LSOAs in London, mid-2011

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The ten LSOAs, outside London, with the highest population density in mid-2011 are shown in table 4, along with their rank in the overall list when London is included.

Table 4: Non-London LSOAs with highest population density, mid-2011

Rank LSOA Population Density (persons per sq. km)
20 Leicester 018B                33,800
24 Brighton and Hove 026B                32,700
40 Brighton and Hove 029C                30,300
53 Leicester 022E                28,500
56 Leicester 017F                28,300
59 Sheffield 074E                28,000
61 Bradford 042B                28,000
83 Brighton and Hove 029D                26,400
87 Leicester 018A                26,300
102 Brighton and Hove 030B                25,500

Table source: Office for National Statistics

Table notes:

  1. Rank given is overall rank when London is included

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The LSOA with the highest population density, outside of London, in mid-2011 was Leicester 018B. This is an area where, approximately, 2,000 people live in 0.06 square kilometres, resulting in a density of approximately 33,800 persons per square kilometre. The four areas of Leicester shown in table 4 are all located around the Spinney Hills area and generally contain streets of terraced housing. Brighton and Hove 026B (and neighbouring 029C) is in the Brunswick area of Hove where a large proportion of the housing consists of Regency era townhouses converted to flats.

Table 5: LSOAs with lowest population density, mid-2011

Rank LSOA Population Density (persons per sq. km)
1 Northumberland 019C                      2.6
2 Northumberland 007D                      4.0
3 Northumberland 003B                      4.3
4 Gwynedd 015D                      4.7
5 Richmondshire 005E                      4.8
6 Northumberland 037E                      4.8
7 Powys 014C                      6.2
8 Northumberland 019D                      6.4
9 Powys 020B                      6.7
10 Powys 020C                      6.8

Table source: Office for National Statistics

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Nine of the top ten least densely populated LSOAs in mid-2011 are in either North East England or Wales, with the top three all being in Northumberland. The least densely populated LSOA in England and Wales is Northumberland 019C with a population density of approximately 2.6 persons per square kilometre in mid-2011. This LSOA includes approximately 670 square kilometres of the area surrounding Kielder Water and some central parts of the Northumberland National Park.  Eight of the top ten areas shown in table 5 are either wholly or partly contained within a National Park area.

Notes for Population Density

  1. Population density is calculated as the population estimate of each SOA divided by its land area in square kilometres. Land area is measured to the mean high water mark for coastal areas and excludes areas of inland water. This is the Eurostat recommended method for compiling population density figures. Land area is obtained from the Standard Area Measurements published on the ONS website.

Comparison with 2011 Census estimates

The mid-2011 census-based population estimates are not directly comparable with the 2011 Census results at LSOA level for the following reasons:

  • The reference point of the two datasets is different. The mid-year estimates refer to 30 June 2011 and the census estimates to 27 March 2011. The mid-year estimates account for any population change that has occurred between these dates.

  • In order to ensure that the 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 LSOA 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 mid-year estimates series at LSOA level uses different geographic referencing for some prison establishments. This was an improvement introduced with revisions published in May 2010 to allocate prisons to the LSOA in which the majority of the prison fell. This allocation of prisons differs from the 2011 Census allocation of prisons in a small number of areas.

Comparison with series rolled forward from 2001 Census

For England and Wales the mid-2011 population estimate, based on the 2011 Census, was 56,170,900. The ‘rolled forward estimate’ for mid-2011 (ie the estimate originally based on the 2001 Census but updated year-on-year to account for population change) was 55,706,700. This implies that the rolled forward series underestimated the population by 464,200 (0.8%).

Further information on the likely causes of the underestimation and how it is broken down at local authority level was published in the report: ‘ Examining the difference between the rolled forward mid-2011 population estimates and the 2011 Census-based MYEs at local authority level (1.19 Mb Pdf) ’.

Comparisons of the mid-2011 Census based LSOA estimates (presented in this release) against rolled forward mid-2011 LSOA estimates can only be made directly for those LSOAs which were not affected by the boundary changes introduced following the 2011 Census. The distribution of the difference in mid-2011 population between the rolled forward and census-based estimates for the 33,519 LSOAs unaffected by the boundary changes is shown in figure 4 below.

Figure 4: Distribution of percentage difference between rolled forward and census-based total population estimates for selected LSOAs, mid-2011

Figure 4: Distribution of percentage difference between rolled forward and census-based total population estimates for selected LSOAs, mid-2011
Source: Office for National Statistics

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The rolled forward estimate was within ±1% of the census-based estimate for mid-2011 in 5,223 LSOAs (15.6%) and within ±5% in 21,696 LSOAs (64.7%). More LSOAs were underestimated than overestimated (54.2% compared to 45.4%) as would be expected given the overall underestimation at national level.

The top ten LSOAs with the highest levels of overestimation of the total population by the rolled forward series are given in table 6 below. All have a percentage difference between the rolled forward and census-based estimates of more than 60% at mid-2011. The majority of these areas are within London, whilst three are within the City of London. This is expected given that the total population of the local authority of City of London was overestimated by 62.5% in the rolled forward estimates. The differences seen in the remaining areas are likely to be due to difficult to measure populations such as students and armed forces.

Table 6: LSOAs with highest percentage difference between rolled forward and census-based estimates, mid-2011

Rank LSOA Percentage Difference
1 Southampton 029C                    98.8
2 Camden 025E                    90.5
3 City of London 001C                    82.8
4 Northampton 015B                    75.7
5 City of London 001E                    75.4
6 Westminster 020B                    75.1
7 City of London 001A                    66.2
8 Forest Heath 006E                    64.0
9 Chorley 006E                    60.7
10 Westminster 003B                    60.3

Table source: Office for National Statistics

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The top ten LSOAs with the highest levels of underestimation of the total population by the rolled forward series are shown in table 7 below. The areas are similar to those with the highest overestimation, including areas within London boroughs, areas with high student populations and one area with a high armed forces population - West Oxfordshire 014C which includes part of RAF Brize Norton.

Table 7: LSOAs with lowest percentage difference between rolled forward and census-based estimates, mid-2011

Rank LSOA Percentage Difference
1 West Oxfordshire 014C -49.9
2 Guildford 012A -49.7
3 Hillingdon 015A -46.3
4 Newham 037A -46.2
5 Welwyn Hatfield 010D -41.2
6 East Riding of Yorkshire 025A -39.8
7 Liverpool 037A -39.2
8 Manchester 019C -38.1
9 Brent 015D -37.3
10 Newham 010A -37.3

Table source: Office for National Statistics

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This report provides a high level summary of the scale of the difference between the new census-based mid-2011 estimates and the estimates that would have resulted from continuing to use the series based on the 2001 Census (the rolled forward estimates). A more detailed analysis of the errors that have accumulated over the decade is required to assess the methodology used to update the estimates annually. This further research is not expected to be completed until 2014.

Small Area Population Estimates for other UK Countries

Population estimates are produced for similar small areas in both Scotland and Northern Ireland, however they are not produced using the same methodology as for Super Output Areas in England and Wales.

National Records of Scotland (NRS) produce population estimates for Scottish Data Zones, which are slightly smaller areas than LSOAs designed to contain approximately 500 to 1,000 household residents. NRS use a cohort component based method to produce estimates for Data Zones, further information on this methodology and the latest estimates (for mid-2011 based on 2001 Census results) are available from their website. These mid-2011 estimates will be subject to scheduled revision following publication of the 2011 Census results for Scotland.

The Northern Ireland Statistics and Research Agency (NISRA) publish population estimates for Super Output Areas in Northern Ireland. These are of similar size to English and Welsh LSOAs with populations of approximately 1,300 to 2,800 with a target size of 2,000. NISRA use a mixed methodology based on both cohort component and ratio change approaches. Further information and the latest estimates published for mid-2010 are available from the NISRA website. Mid-2011 estimates are currently planned for publication at the end of 2013/14.

A paper, Small Area Population Estimates across the UK which provides a broad description of the different methodologies used to produce small area population estimates in each constituent country of the UK, is also available on the NISRA website.

Publications in 2013

The list below shows the other small area population estimates products for England and Wales which are planned for publication in 2013. The majority of the dates given below are provisional. Final confirmed dates will be available on the UK National Statistics Publication Hub release calendar at least four weeks before publication.

  • Primary Care Organisation (PCO) population estimates, mid-2011 (final) – these estimates have been released alongside this publication, so are available on the ONS website.

  • Small area population estimates for wards, parliamentary constituencies and National Parks, mid-2011: May/June 2013.

  • Super Output Area (SOA) population estimates, mid-2002 to mid-2010 revised: August/September 2013.

  • Super Output Area (SOA) population estimates, mid-2012: September/October 2013.

  • Small area population estimates for wards, parliamentary constituencies and National Parks, mid-2002 to mid-2010 revised: November/December 2013.

  • Small area population estimates for wards, parliamentary constituencies and National Parks, mid-2012: November/December 2013.

Further research work on small area population estimates is planned to be completed following the publication of the products listed above. This is likely to include:

  • Detailed assessment of the difference between 2011 Census SOA population estimates and the estimates for mid-2011 based on the 2001 Census.

  • Review of the methods used to produce small area population estimates in the light of the results of the 2011 Census.

 

Background notes

  1. National Statistics are produced to high professional standards set out in the Code of Practice for Official Statistics. They undergo regular quality assurance reviews to ensure that they meet customer needs. They are produced free from any political interference.

  2. An Overview of Population Statistics is available on the ONS website.

  3. Mid-2011 population estimates for Super Output Areas in England and Wales are available from the ONS website.

  4. Published tables include population estimates for middle layer Super Output areas (MSOAs) and lower layer Super Output Areas (LSOAs) by five year age/sex groups.

  5. Population estimates for MSOAs and LSOAs will also be made available by single year of age and sex to enable and encourage further calculations and analysis.

  6. Rolled forward mid-2011 LSOA population estimates used to assess the difference between the 2011 Census based estimates and the previous series based on 2001 Census data are also published as part of this release. These are not the official population estimates for mid-2011 and have only been published as supporting information.

  7. A report describing the methodology used to create the SOA estimates is available on the ONS website.

  8. This is the first release of mid-2011 population estimates for Super Output Areas in England and Wales. No revisions of this dataset have been made.

  9. Mid-2011 population estimates for England and Wales and for local authorities are also available on the ONS website.

  10. Details of the policy governing the release of new data are available by visiting www.statisticsauthority.gov.uk/assessment/code-of-practice/index.html or from the Media Relations Office email: media.relations@ons.gsi.gov.uk

    The United Kingdom Statistics Authority has designated these statistics as National Statistics, in accordance with the Statistics and Registration Service Act 2007 and signifying compliance with the Code of Practice for Official Statistics.

    Designation can be broadly interpreted to mean that the statistics:

    • meet identified user needs;
    • are well explained and readily accessible;
    • are produced according to sound methods; and
    • are managed impartially and objectively in the public interest.

    Once statistics have been designated as National Statistics it is a statutory requirement that the Code of Practice shall continue to be observed.

Statistical contacts

Name Phone Department Email
Pete Large +44 (0)1329 444661 Population Estimates Unit pop.info@ons.gsi.gov.uk
Get all the tables for this publication in the data section of this publication .
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