1. Methodology background


 National Statistic   
 Survey name  UK Electoral Statistics
 Frequency  Annual
 How compiled  Based on third party data
 Geographic coverage  UK, local authority, Parliamentary constituency
 Last revised  22 March 2019
 Related bulletin  Electoral statistics for UK

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2. About this Quality and Methodology Information report

This quality and methodology report contains information on the quality characteristics of the data (including the European Statistical System five dimensions of quality) as well as the methods used to create it.

The information in this report will help you to:

  • understand the strengths and limitations of the data

  • learn about existing uses and users of the data

  • understand the methods used to create the data

  • help you to decide suitable uses for the data

  • reduce the risk of misusing data

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3. Important points

  • Electoral statistics are National Statistics and are published for the UK, its constituent countries, English regions, local government areas and Parliamentary constituencies.

  • They provide annual counts of the number of people who are registered on electoral rolls on 1 December each year, but do not provide details on the personal characteristics of the electorate, nor the size of the population eligible to vote.

  • Statistics are collected for two main classifications of voters: the “Parliamentary electorate” and the “European and local government electorate.”

  • Attainers are people who reach the age of 18 years during the currency of the register (or registration) year; they are included in electoral statistics for both the Parliamentary electorate and the European and local government electorate.

  • Electoral statistics are used by Boundary Commissions, the Electoral Commission and central government to help with the improvement of electoral policies and for statutory reviews of Parliamentary constituency boundaries.

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4. Output quality

We have developed Guidelines for measuring statistical quality based upon the five European Statistical System (ESS) quality dimensions. This report addresses the quality dimensions and important quality characteristics, which are:

  • relevance

  • accuracy and reliability

  • output quality

  • coherence and comparability

  • concepts and definitions

  • geography

  • accessibility and clarity

  • timeliness and punctuality

  • why you can trust our data

More information is provided about these quality dimensions in the following sections.

Overview

Electoral statistics for the UK are usually published annually around February or March.

There are two main classifications of voters: the “Parliamentary electorate” and the “European and local government electorate”. Commonwealth citizens, British citizens and citizens of the Republic of Ireland who are normally resident in the area on the qualifying date and who have reached the eligibility age during the electoral register’s currency are entitled to vote.

The Parliamentary electorate includes overseas electors but excludes Peers and EU citizens. The European and local government electorate includes Peers and EU citizens but excludes overseas electors. Overseas electors are not resident in the UK but can vote in a Parliamentary election if they have previously been resident in the UK and included in the electoral register (unless they were too young to register). They are registered to vote in the same Parliamentary constituency as before they went abroad.

An attainer is a person who attains the age of 18 years during the currency of the register and is entitled to vote at an election on or after his or her 18th birthday for Parliamentary and local government elections. This only applies to England, Wales and Northern Ireland. The voting age for the Scottish Parliament and local government elections in Scotland was lowered in 2015 to the age of 16 years.

Introduction of Individual Electoral Registration (IER) in 2014 has brought about new administrative practices. This may have changed the proportion of those eligible that are registered to vote, however, does not change who is eligible to vote.

For England and Wales, electoral statistics are taken from data supplied to the Office for National Statistics by local Electoral Registration Officers (EROs). Data for Scotland are similarly collected by National Records of Scotland (NRS). Data for Northern Ireland are collected by the Electoral Office for Northern Ireland (EONI).

The main reasons why the registered numbers of electors in an area can change from year to year are:

  • a change in the size of the population who are entitled to vote; for example, due to international migration, internal migration or deaths

  • a change in the proportion of the eligible population who actually register to vote; for example, more people registering as a result of better canvassing or due to an election

  • changes to the franchise; for example, in Scotland in the summer of 2015, those aged 16 to 17 years became able to vote in Scottish Parliamentary elections and local government elections

Uses and users

The statistics are compiled from data supplied to us by EROs and are used by government, including Cabinet Office, the Electoral Commission and the Boundary Commission. They are also used by Members of Parliament and the general public.

Strengths and limitations

Strengths

  • Electoral statistics represent the most accurate count possible of the number of electors on 1 December, based on the information provided on the “Summary of Register of Electors” by the EROs for each local authority.

  • Electoral statistics for the UK are usually published annually around February or March, two months after the reference date.

  • Since 2001, electoral statistics have been derived using data supplied on a reference date of 1 December and the methodology has remained consistent.

Limitations

  • Electoral statistics provide counts of registered but do not provide an estimate of the population eligible to register.

  • The data used to produce this release do not include any information about the age or sex of electors.

Recent improvements

The 2019 release of Electoral statistics includes additional tables previously released on an ad-hoc basis. These additional tables are:

  • Parliamentary electors living overseas for England (regions) and Wales

  • Anonymous electors for England (regions) and Wales

  • Electors opted out of the open register for local authorities in England and Wales

  • Parliamentary electors for local authorities in England and Wales

In addition, there have been several changes to local authority names, codes and boundaries. These are summarised in Table 1. The new local authority codes for Fife, and Perth and Kinross are used in all output tables; the new local authorities in England are shown in Table 3 of the datasets accompanying this release (post-April 2019 local authorities).

Data processing for the 2019 release of Electoral statistics was the first to use a new Python-based processing system. Quality assurance work confirmed that this produced the same estimates as the previous coding system and had not made any changes to the methodology, simply making production more efficient.

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5. Quality characteristics of the electoral statistics data

This section provides a range of information that describes the quality and characteristics of Electoral statistics and identifies issues that should be noted with these data.

Relevance

(The degree to which statistical outputs meet users’ needs.)

We collate and publish electoral statistics, which are used by central government departments (such as Cabinet Office) and the Electoral Commission, and by Boundary Commissions when reviewing boundaries to ensure a fair representation in Parliament. Other users include Members of Parliament and the general public.

The electoral statistics meet the important user needs in terms of coverage and detail. We liaise closely with the Electoral Commission and Cabinet Office before data collection commences. The format and details to be collected on the “Summary of Register of Electors” supplied by the Electoral Registration Officers (EROs) to us are specified by these main users, as are the boundaries that the statistics are published on. This ensures that user needs are met.

Accuracy and reliability

(The degree of closeness between an estimate and the true value.)

Electoral statistics represent the most accurate count possible of the number of electors on 1 December, based on the information provided on the “Summary of Register of Electors” by the EROs for each local authority.

For England and Wales, we follow up missing or incomplete returns. If no return is received prior to publication, data from the previous year are used and a footnote against the published table identifies these areas to users.

National Records of Scotland (NRS) and the Electoral Office for Northern Ireland (EONI) perform similar follow-up procedures on the information provided by the EROs for areas in Scotland and Northern Ireland respectively. We collate and publish the statistics for the UK constituent countries.

In England, Wales and Scotland a rolling registration system was introduced in 2001 whereby EROs update registers on a continuous basis. From 2014, a system called Individual Electoral Registration (IER) was also introduced, which replaced the previous household-based registration system with one in which every individual must register independently. The introduction of IER allows individuals more control over the registration process and increases accuracy by ensuring that the identity of every applicant is verified (using information such as date of birth and National Insurance number) before their details are added to the electoral register.

In Northern Ireland, a system of continuous registration was introduced in 2007, which provides monthly updates to the electoral register. A revised register, incorporating all the updates, is published each year on 1 December. However, the summary statistics published reflect the operational date of 1 December and there are no plans for us to publish updates between the annual publications.

For England, Wales and Scotland, the residence qualification requires a person to be normally living at the address on the qualifying date, even if temporarily absent. People having more than one place of residence, such as students, may therefore be included on more than one register but are only entitled to vote in one constituency in a general election. In Northern Ireland, the residence qualification requires a person to have resided in Northern Ireland for the previous three months before he or she can register. Students in Northern Ireland can register at their home address or term-time address, but not both.

The latest information on the quality of electoral registers following the introduction of IER is available on the Electoral Commission website, where you can read the latest on electoral registration research.

There are no statistical quality measures, such as standard errors, relating to the accuracy of electoral statistics, as the statistics are aggregated counts and no estimation is involved. The main threats to the accuracy of electoral statistics are non-response and clerical error associated with the completion of the “Summary of Register of Electors” and processing error when the statistics are compiled. Quality checks and procedures, such as consistency checks on calculations, are in place to minimise these threats.

Corrections to errors with published electoral statistics have occasionally been necessary in the past. These corrections were released promptly and in an open and transparent manner and users were alerted in line with our policy on revisions and corrections. Any future revisions and corrections would also follow this policy.

Coherence and comparability

(Coherence is the degree to which data that are derived from different sources or methods, but refer to the same topic, are similar. Comparability is the degree to which data can be compared over time and domain, for example, geographic level.)

Electoral statistics for 2018 were published on 22 March 2019, containing data for the UK, England, Wales, Scotland and Northern Ireland. The reference date for all countries was 1 December 2018.

Since 2001, electoral statistics have been derived using data supplied on a reference date of 1 December and the methodology has remained consistent. Prior to 2001, the reference date for the electoral statistics was 16 February.

Between 2012 and 2014, the reference dates of electoral statistics in different areas of the UK differed from the standard 1 December due to a number of reasons:

  • because of the Police and Crime Commissioner elections held in November 2012, the 2012 electoral statistics for England (excluding London) had a reference date of 16 October 2012; all other areas of the UK had a reference date of 1 December 2012

  • because of preparations for the introduction of Individual Electoral Registration (IER), the 2013 electoral statistics had a reference date of 17 February 2014 in England, 10 March 2014 in Wales and Scotland, and 1 December 2013 in Northern Ireland

  • because of the later introduction of IER in Scotland following the Scottish Independence Referendum, the 2014 electoral statistics had a reference date of 2 March 2015 in Scotland; all other areas of the UK had a reference date of 1 December 2014

Changes in the electorate can result directly from changes in legislation. For example, in 2004, 10 countries joined the European Union (EU) and it expanded again in 2007 and in 2013. Each country accepted into the EU increased the number of people eligible to vote in the European and local elections in the UK.

In 2015, the voting age for the Scottish Parliament and local government elections in Scotland was lowered to the age of 16 years. The voting age for local government electors in England, Wales and Northern Ireland and for all Parliamentary electors throughout the UK remained at the age of 18 years. The tables in our Electoral statistics 2015 release included the younger attainers in the local government areas of Scotland for the first time.

This product is the official set of electoral statistics for the UK and constituent countries. Users sometimes compare electoral statistics with other data sources, for example, population estimates, administrative records, or anecdotal evidence. Comparisons between datasets should be treated with caution, as there are always definitional differences in the data collected. Other data sources may cover only a subset of the electoral register, or may include those not registered to vote.

The electoral statistics provide information on the number of people registered to vote. This is not the same as the resident population aged 18 years or over for a number of reasons, not least the recent lowering of the voting age for local government elections in Scotland. For example, not everyone who is usually resident is entitled to vote, not everyone who is entitled to vote is registered to vote and people who have more than one address may register in more than one place.

Furthermore, there is inevitably some double-counting of the registered electorate, as EROs vary in how quickly they remove people from the registers after they have moved away from an area, or after they have died. These factors have a differential impact from area-to-area.

Similarly, registration rates calculated by dividing electoral counts by population estimates will give only an approximation. Further information can be found in the Electoral Commission’s detailed study Electoral Registration in 2000 (PDF, 160KB).

Accessibility and clarity

(Accessibility is the ease with which users are able to access the data, also reflecting the format in which the data are available and the availability of supporting information. Clarity refers to the quality and sufficiency of the release details, illustrations and accompanying advice.)

Electoral statistics from 2012 onwards are available on the UK electoral statistics page of our website. Statistics for 2000 to 2011 are available on the ONS archive website. Statistics for 1997 to 1999 are available on request by contacting the Population Estimates Unit by email pop.info@ons.gov.uk. Some data are also available for the period 1991 to 1996 and further information on this is also available from the Population Estimates Unit.

Links from the UK government statistics release calendar make the release date and location of each new set of statistics clear. The statistics can be downloaded free of charge in Microsoft Excel format. From 2011 the statistics are also accompanied by a statistical bulletin.

Most queries can be answered from the website datasets. Any additional enquiries regarding electoral statistics can be made via email pop.info@ons.gov.uk or telephone +44 (0)1329 444661.

Our recommended format for accessible content is a combination of HTML web pages for narrative, charts and graphs, with data being provided in usable formats such as CSV and Excel. Our website also offers users the option to download the narrative in PDF format. In some instances, other software may be used, or may be available on request. Available formats for content published on our website but not produced by the ONS, or referenced on our website but stored elsewhere, may vary. For further information please refer to the contact details at the beginning of this report.

Information regarding conditions of access to data:

In addition to this quality and methodology information, basic quality information relevant to each release is available in the quality and methodology section of the relevant statistical bulletin, available from the Electoral registration section of our website. For releases prior to Electoral statistics, UK: 2018, quality information relevant to each release was made available in the quality and methodology section of the relevant statistical bulletin.

Timeliness and punctuality

(Timeliness refers to the lapse of time between publication and the period to which the data refer. Punctuality refers to the gap between planned and actual publication dates.)

Electoral statistics for the UK are usually published annually around February or March, two months after the reference date. This time lag reflects the availability of data in the form of a completed response from the ERO for each local authority and the time taken to process the data and compile the statistics. Electoral statistics are available within the timescale required by the Boundary Commission to allow for their use in boundary reviews.

The publication of electoral statistics is only later than the planned date if essential data used to calculate the estimates are not received or if substantial problems are encountered with processing the data. Owing to the late availability of data from some suppliers, the release date for the December 2016 estimates was moved from the provisional date of 23 February 2017 to 16 March 2017. The release date of 16 March 2017 was confirmed, via our release calendar on 30 January 2017.

In previous years, the planned publication date, as entered into the release calendar, has always been met but in the unlikely event of a change to the release schedule, an announcement will be made at least two weeks in advance, as set out in the Code of Practice for Statistics.

For more details on related releases, the UK government statistics release calendar is available online and provides 12 months’ advance notice of release dates. In the unlikely event of a change to the pre-announced release schedule, public attention will be drawn to the change and the reasons for the change will be explained fully at the same time, as set out in the Code of Practice for Statistics.

Concepts and definitions (including list of changes to definitions)

(Concepts and definitions describe the legislation governing the output and a description of the classifications used in the output.)

Electoral statistics refer to the number of people who were registered to vote if an election had been held on 1 December of the reference year. This is the new reference date for electoral registers. Prior to 2001, the annual canvass resulted in registers that came into effect on 16 February.

There are two main classifications of voters: the Parliamentary electorate and the European and local government electorate. Commonwealth citizens, British citizens and citizens of the Republic of Ireland who are normally resident in the area on the qualifying date and who have reached the eligible age during the electoral register’s currency, are entitled to vote. However, further eligibility criteria for the two classifications are different.

The Parliamentary electorate includes overseas electors but excludes Peers and EU citizens. The European and local government electorate includes Peers and EU citizens but excludes overseas electors. Overseas electors are not resident in the UK but can vote in a Parliamentary election if they have previously been resident in the UK and included in the electoral register (unless they were too young to register). They are registered to vote in the same Parliamentary constituency as before they went abroad.

Attainers are included in electoral statistics for both the Parliamentary electorate and the European and local government electorate. For Parliamentary elections in all constituent countries of the UK, an attainer is a person who attains the age of 18 years during the currency of the register and is entitled to vote at an election on or after his or her 18th birthday. For England, Wales and Northern Ireland, this is also the case for local government elections.

In 2015, the voting age for the Scottish Parliament and local government elections in Scotland was lowered to the age of 16 years. For these elections an attainer is a person who attains the age of 16 years during the currency of the register and is entitled to vote at a local election in Scotland on or after his or her 16th birthday. Additional information on eligibility and electoral law can be found on the Electoral Commission website.

Electoral statistics are published for local authorities and Parliamentary constituencies. Boundary changes are reflected in electoral statistics following the requirements of the Electoral Commission (see the Comparability section). Reflecting boundary changes ensures the data are fit for purpose for the Boundary Commission and the Electoral Commission. Such changes do not impact on the quality of the electoral statistics in any particular year. However, the statistics cannot be directly compared between years where boundary changes have taken place. Metadata published alongside the tables indicate where the statistics are published on new boundaries.

Geography (including list of changes to boundaries)

Electoral statistics are produced for local government areas (for local government electors), for Parliamentary constituencies (for Parliamentary electors) and at a regional level when the data pose a disclosure risk.

Users should be mindful of boundary changes when comparing time series of electoral statistics. The length of the comparable time series is dependent on the frequency of local authority and Parliamentary constituency boundary changes. Electoral statistics by local authority are published on the boundaries in place on the reference date. Electoral statistics by Parliamentary constituency are published on the boundaries required by the Electoral Commission and for some years these statistics have been published on two sets of boundaries. The boundaries used are as published on the ONS geoportal.

On 1 April 2015, the number of local government districts in Northern Ireland was reduced from 26 to 11. This change is reflected in the 2015 and 2016 Parliamentary electoral statistics for Northern Ireland, which show data for the 11 new areas. Although some of these new districts are exact aggregates of the former districts, many are not, preventing a direct comparison with data from previous years. Guidance on production of official statistics for the 11 new local government districts (LGD2014) is available for users from the Northern Ireland Statistics and Research Agency (NISRA).

Parliamentary constituency boundaries have remained unchanged since 2010.

Local government boundaries changed in April 2019 following the mergers of some local authorities to form new local authorities as set out in Table 3. Where practical, data on both the old and new local authorities have been published as part of the 2019 release of Electoral statistics.

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6. Methods used to produce electoral statistics

In England and Wales, the Office for National Statistics (ONS) requests data on the numbers of Parliamentary and European and local government electors as at 1 December of the reference year from the Electoral Registration Officer (ERO) of each local authority area.

Raw data counts supplied to the ONS by each ERO are quality-assured and any unusual or unexpected figures are queried with the ERO before the data are used in the compilation of the statistics. The counts of electors and attainers are aggregated to produce electoral statistics by the required geographies.

Missing or incomplete returns are followed up by the ONS. If no return is received prior to publication, either data from the previous year are used or the data are compiled from data held by the relevant Boundary Commission. A footnote against the published table identifies these areas to users.

The ONS produce UK-level electoral statistics using data for Scotland and Northern Ireland, produced by National Records of Scotland (NRS) and the Electoral Office for Northern Ireland (EONI) respectively. NRS and EONI follow similar procedures and methods as those used by the ONS for the England and Wales statistics.

Electoral statistics are usually published annually at the end of February each year, approximately three months after the reference date of 1 December. However, due to the introduction of Individual Electoral Registration (IER), the 2014 electoral statistics for Scotland have a reference date of 2 March 2015.

Quality assurance

In addition to the quality assurance carried out during the compilation process, the statistics are reviewed by the Boundary Commissions for England, Wales and Scotland prior to publication. They provide quality assurance based on their expert knowledge and against data held by them at smaller geographical levels.

Statistical disclosure control

Statistical disclosure control methodology is not necessary as the counts of electors at local authority and Parliamentary constituency level are large enough to ensure that information attributable to an individual cannot be identified in the published outputs.

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7. Other information

Assessment of user needs and perceptions

We regularly consult users on our statistical work programme. Results of these are available on the consultation section of our website.

Main users of electoral statistics, including the Electoral Commission, Boundary Commissions and Cabinet Office, are consulted annually on their requirements with regular meetings being held. In particular, we liaise closely with the Electoral Commission and Cabinet Office before data collection commences and the format and details of the data collected each year are specified by these main users.

Local area users are consulted through the Central and Local Information Partnership (CLIP) Population Sub-group. The aim of the CLIP Population Sub-group is to improve communication between the Office for National Statistics (ONS) and some users of population statistics produced by ONS. Minutes from these meetings are published on the Population Statistics discussion board of the StatsUserNet website.

Useful links

ONS electoral statistics

Electoral Commission

Boundary Commissions for:

England

Wales

Scotland

Northern Ireland

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Contact details for this Methodology

Neil Park
pop.info@ons.gov.uk
Telephone: +44 (0) 1329 444661