Conduct of the 2021 Censuses in the UK: November 2019 progress update

This is the second progress report on the statement of agreement (PDF, 164KB) between the National Statistician and the Registrars General for Scotland and Northern Ireland. It covers the conduct of the 2021 censuses, which are intended to be carried out simultaneously throughout the UK.

This report shows the progress made so far on each aspect of the census that the three census offices are aiming to harmonise. These aspects were set out in the statement of agreement.

Consistent, coherent and accessible statistics

The Census 2021 outputs should constitute consistent, coherent and accessible statistics for the UK, individual countries and geographic areas within each country.

Progress as at 1 November 2019

Each of the UK census offices (the Office for National Statistics (ONS), the National Records of Scotland (NRS) and the Northern Ireland Statistics and Research Agency (NISRA)) ran separate census outputs strategy consultations. All three offices have used a broadly consistent approach.

The ONS response and the NRS response to their respective consultations are available. NISRA’s response will be published in early 2020.

The outputs strategy consultations collected valuable user feedback that the census offices will use to shape the design and delivery of outputs that are coherent and accessible. The ONS is currently planning stakeholder engagement activities to help develop a detailed plan for output content.

The census offices’ main aim is to produce statistical outputs that will meet user information needs and will be flexible, timely and accessible. This is outlined in each of the outputs strategy consultations. These consultations, and active engagement with users up to and beyond the 2021 censuses, will ensure each office is well informed of user requirements.

In addition to the consultations, during Phase 1 of the 2021 censuses National Statistics accreditation process for the UK, the Office for Statistics Regulation recommended that the census offices should consider how best to engage with users and stakeholders of UK census data and statistics users and co-ordinate activities as appropriate. The ONS, NRS and NISRA will work together to ensure UK comparability of census results, where possible and appropriate.

Each census office is planning to publish the first census outputs more quickly than for the 2011 censuses. Data users will be able to easily locate and access the outputs. There are proposed facilities for users to create their own data products that have, from a statistical disclosure control (SDC) perspective, been appropriately protected. The census offices will co-ordinate SDC methodologies where practicable to do so.

On behalf of the census offices, the ONS has commissioned an exploratory piece of work with the UK Data Service to assess harmonisation across the UK census offices. We will use the results from this to develop plans for providing user access to UK harmonised census data from a single point of access.

Common definitions and classifications

Common definitions and classifications, typically based on international standards, should be agreed, used and published (this includes a common population base).

Progress as at 1 November 2019

For questions and topics that are comparable across the UK, the census offices will agree a set of common definitions and classifications to use. This is with the aim of publishing consistent census outputs across the UK. Where possible, these definitions and classifications will be based on international standards. This will ensure that the UK meets its international obligations for producing census statistics.

The ONS will chair workshops to assess the harmonisation of questions, definitions, classifications and output content. Representatives from the ONS, NRS, NISRA, the Welsh Government and Government Statistical Service harmonisation teams will attend. The workshops will begin in early 2020, focusing on definitions to start with.

Common topics and questions

Common topics and questions should be agreed wherever possible, with the intention of making available consistent census outputs across the UK.

Progress as at 1 November 2019

In terms of question development harmonisation, the focus is on outputs from the data collected. The ONS, NRS and NISRA have worked to ensure questions are directly comparable. The exception is where there is a clear evidence-based need for them to be different. We have also worked to develop supporting question guidance, sharing materials to ensure the guidance is only different by design.

Each census office has undertaken a programme of development across all questions that were proposed as new or for change. This work fed into the UK-wide topic groups and the monthly and weekly catch-up meetings for the three offices. Additionally, the purpose of the quarterly UK Question Development Working Group was to revise and update the joint harmonisation plan and joint research plan.

There have been several cross-country tests and stakeholder workshops. These have included large-scale quantitative tests on the sexual orientation and gender identity topics, and joint stakeholder events and testing for the armed forces question.

This has contributed to the development of new questions and methods for the armed forces and sexual orientation topics that will provide comparable outputs across the countries. Due to country-specific user needs and research findings, there will also be a gender identity question in England and Wales, a trans status question in Scotland, and neither in Northern Ireland. These questions were designed to meet the user need identified in that country.

The wording of some questions will more closely align than in 2011, for example, in the main language question. However, others may align less than in 2011, for example, the qualifications question.

Census date

The three censuses should be carried out with reference to the same date in 2021.

Progress as at 1 November 2019

The timelines differ for each census office as to when the respective Census Order, which includes the date of the census (21 March 2021), is to be laid in their respective legislatures.

At the ONS, the aim is for the Census Order for England and Wales to be laid in Parliament in early 2020.

The Census Order for Scottish Parliament will be laid in the first half of 2020.

In Northern Ireland, the necessary legislation to conduct a census is normally taken through the Northern Ireland Assembly. However, as there is currently no sitting Assembly, NISRA is pursuing with the Northern Ireland Office a process for the Secretary of State for Northern Ireland to sponsor the legislation in Westminster.

Methodologies and statistical procedures

The statistical procedures applied to the census data, such as methodologies for statistical disclosure control and estimation, should be evaluated, tested and agreed in advance of the census, and co-ordinated across the UK.

Progress as at 1 November 2019

Development of statistical methods for the censuses (including statistical disclosure control (SDC), edit and imputation (E&I), coverage assessment and coverage adjustment) is progressing. Each census office participates in UK-wide working groups associated with the main data processing areas. These groups facilitate information sharing and encourage harmonisation of methods where appropriate.

NISRA will conduct census data processing independently for the first time in 2021. The various methods involved will be largely based on those that the ONS developed and implemented during processing of Northern Ireland data for the 2011 Census. The methods associated with the early processing stages of removing false records and reconciling multiple responses are well established. They will be broadly similar to those that the ONS and NRS use.

For the 2021 censuses, each census office is using targeted record swapping and the cell key perturbation method for SDC. This is ensuring broad harmonisation of the methodology across the UK. However, each reserves the right to use different parameters, that is, higher or lower levels of swapping, different variables for targeting, and different perturbation matrices.

Specialist software will underpin E&I in each census office. This ensures a consistent approach to the E&I of data from the 2021 censuses across the UK.

Regarding coverage assessment and adjustment, NRS and NISRA propose to use the established dual-system estimation method. The ONS plans to use a model-based approach that allows it to assess under-coverage for all of England and Wales at once. For adjusting the data for under-coverage, NRS will use the 2011 calibration method. NISRA is likely to use elements of the 2011 calibration method supplemented by intelligence from administrative data. The ONS will use an algorithmic method based on combinatorial optimisation. The outcomes will be similar, and we are staying informed through working groups.

While each census office collects information relating to the same underlying concept, there are differences in the questions and the way they are asked. This means that, by default, there are differences in the way the data are processed. Additionally, how and where administrative data are used in the process varies between the offices. Each census office is assessing the suitability of the administrative data it is using. This will ensure that when combined with the census response data and the designed statistical methods it will support the production of robust outputs.

The ONS is developing its approach to quality assure the census data and a first set of checks and tools is being implemented for the census rehearsal. A proposal for the methods for quality assurance (QA) is being published for user comment in January 2020. Focus groups are being arranged with local authority users to understand their requirements for information on quality.

NRS shared its Statistical Quality Assurance Strategy with its main user group and will be publishing it before the end of the year.

The approach to QA of census data by NISRA will be underpinned by the wider availability of administrative data sources, draw upon the effective QA methods implemented in the 2011 Census, and consider some of the tools being developed by the ONS and NRS.

Each census office contributes to the UK Quality Assurance Harmonisation Group. This has been set up to help ensure approaches to this aspect of census work are as similar as possible.

Sharing skills and experiences

Recognising their common requirements, the census offices will share skills and experiences and endeavour to exploit economies of scale wherever possible.

Progress as at 1 November 2019

The memorandum of understanding between the ONS and NISRA has facilitated strong and effective working relationships in relation to our respective 2019 census rehearsals and 2021 censuses.

We have successfully developed and implemented a number of shared services (for example, questionnaire management, contact centre and a field work management tool). Working closely together during the operational phase of the rehearsal ensured we were able to effectively manage incidents and issues.

Memorandums of understanding between the ONS and NRS have ensured we are able to work together effectively. This has included sharing lessons learned and findings from research in areas such as question and questionnaire design. We have also shared requirements for procurements such as the contact centre.

In addition, there is a joint Field Operations Group that meets quarterly to share operational designs and best practice. Weekly catch-up meetings during the operational phase of the census rehearsals allowed us to share experience and progress.

Use of administrative data

The census offices will work together to exploit, and make greater use of, administrative data sources.

Progress as at 1 November 2019

The UK Population and Censuses Strategic Group is now the main forum for discussing the harmonisation of the use of administrative data for UK population statistics. It has a wide remit including:

• proposed improvements to the existing England and Wales population statistics system

• making use of administrative data in the 2021 censuses

• co-ordinating plans across the UK to feed in to recommendations for future censuses

The group also covers the prioritisation of data acquisition and potential for sharing data across countries to improve the infrastructure for producing UK statistics.

Each census office is part of the four nations Administrative Data Research Group. This group meets twice a year to share information and best practice on effectively integrating administrative data in the census process.

Each census office contributes to the Devolved Administration Joint Working Group. This group meets monthly to discuss the ONS’s acquisition of data through the Digital Economy Act 2017 and how this may support devolved nations.

Publicity campaigns

The census offices will endeavour to ensure that the publicity campaigns for each census complement each other.

Progress as at 1 November 2019

The planning towards the 2021 censuses campaign has started and the rehearsal evaluation will play an important part in determining the nature of the campaign.

The census offices are working closely together, sharing planned marketing and communications activity and feedback on rehearsal evaluation, and planning for 2021. The offices have a monthly phone call (the frequency of which was increased to weekly during the rehearsal) to share information on planned campaigns.

NISRA is working with a contracted agency in Northern Ireland to co-ordinate and carry out the publicity and advertising campaign for the 2021 Census.

The ONS is working with a communications agency and OmniGov, the government-appointed media buying agency, to develop and deliver the advertising and wider campaigns for the census. The ONS is also starting work on planning the printed materials needed to support census operations.

ONS and NISRA are working together to ensure that marketing and advertising materials developed for the census campaign are harmonious in England, Wales and Northern Ireland. The three census offices will keep a degree of consistency between the campaigns for the 2021 censuses, while adapting their approaches to suit local conditions and audiences. This will maximise the effectiveness of UK-level advertising.

UK harmonisation

To promote UK harmonisation, every effort will be made to reach agreement through the cross-working mechanisms of the three census offices and any differences of opinion will be discussed and resolved at the UK Census Committee.

Progress as at 1 November 2019

The Harmonisation Working Group meets regularly with the aim of maximising harmonisation across the UK. Any issues that the group is unable to resolve are escalated to the UK Census Committee for resolution.