Assessment of compliance with the Code of Practice for Statistics – 2021 Census in Northern Ireland

17 November 2021
Last updated:
25 July 2022



The Census is one of the most important sources of data and statistics, informing decisions about almost every aspect of life within the UK. It is of fundamental importance in allocating billions of pounds to local areas by the UK government and devolved administrations, as well as grants to voluntary sector organisations for example. The Census helps every person in the UK get a better understanding of the places in which they live and work.

The real value of the Census will be realised on the release of Census outputs. The Northern Ireland Statistics and Research Agency (NISRA) will have to deliver high quality data and statistics in a variety of forms to support the wide range of different uses required. It is essential that the data and statistics from the 2021 Census in Northern Ireland are reliable and provide valuable insights, meeting the rigorous standards of trustworthiness, quality and value outlined in the Code of Practice for Statistics. The 2021 Census was taken during a national COVID-19 lockdown in Northern Ireland and, as such, captured data on individuals and households at a very unique period of time. Consideration and understanding of the quality and value of Census data and how users’ needs may or may not be met will be especially important in these circumstances.

This is the second assessment report and many of our considerations and judgements build on the preliminary findings as reported in our earlier assessment report published in October 2019. Our preliminary findings, and the last published update of progress – from September 2020 – can be found in . Since then, we have worked closely with NISRA to understand how it has taken forward actions based on our earlier findings and progressed its plans to deliver high quality, valuable Census outputs. This report identifies areas of strength, good practice and innovation in NISRA’s Census planning and development as well as identifying some areas where improvements need to be made.

As with the earlier phase of this assessment, NISRA published a report providing an update on its progress and how its plans and developments align with the standards of the Code. The approach of sharing and explaining this publicly echoes the key aspects of the Code, such as transparency and accountability, and the assessment team recognises this positive communication with stakeholders.

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Understanding the context for Census 2021

Communicating the impacts of COVID-19

The 2021 Census in Northern Ireland was undertaken during the COVID-19 pandemic and NISRA had to respond to various unexpected challenges to successfully, and safely, deliver live Census collection operations at this unprecedented time. To manage and mitigate risks to Census data, NISRA adapted its systems and provided additional support to respondents to best capture accurate data. For example it adapted the development of its address register, using online tools and utilising administrative data, to enhance the accuracy and coverage of data on the status of addresses to best inform field operations. NISRA also took steps to support data collection for respondents. For example, for students in Northern Ireland, NISRA modified the Census electronic questionnaires and, in conjunction with the two main universities in Northern Ireland, provided additional support on how those individuals should complete their Census returns.

Undertaking Census during COVID-19, however, meant that data on topics such as employment, economic activity, travel, and household status may well be unusual or changed. Census data will reflect the population of Northern Ireland at this rather unique point in time and data users’ needs, such as those of local service planners, may no longer be met from the data collected in 2021. NISRA is currently processing and assuring the quality of data collected during Census and will assess how data have been affected and consider what steps it may have to take to address any unmet user needs.

NISRA launched its Census outputs consultation on 1 October 2021 and, as part of the consultation materials, NISRA highlighted where Census data will likely be affected. Through the consultation it will collect users’ views on their information needs on affected Census topics and NISRA should respond to these within its decision making on Census outputs when it publishes its consultation response in January 2022. Information on where Census data will likely be affected, albeit at a high-level, is not available to users outwith the consultation materials and therefore is not easily accessible.

There is much interest from users and stakeholders on data impacts from COVID-19 – or on other factors such as the UK leaving the European Union. Clearer communication and more easily accessible information of the impact on Census data and NISRA’s plans to address any unmet user needs – even where specific solutions or commitments to deliver cannot yet be made – would aid transparency and assure users on the quality and value of forthcoming Census outputs.

To date, NISRA has made little information widely available on the steps it is taking to investigate, or otherwise meet, user needs for data affected by COVID-19. This is a significant gap in the assurances offered by NISRA on its plans to address impacts on data.

Finding 1

In order to support society’s need for information, NISRA needs to clearly communicate how 2021 Census data may be impacted by COVID-19 and how it plans to address any unmet user needs. NISRA should ensure this information is communicated in an accessible and timely way, being open on plans, developments and progress even where definitive answers or solutions are still being sought.

Census and population estimates for the rest of the UK

In July 2020, National Records of Scotland (NRS) announced that Scotland’s Census would be moved by a year to March 2022 due to the impact of COVID-19. This difference of Census dates across the UK will have further impacts on population data, in particular for UK Census data and for plans about how UK population estimates for 2021 will be provided.

The three Census offices have made commitments to work collaboratively to understand and address the needs of users of UK data, most recently in the progress update on the Conduct of the censuses across the UK. NISRA already works closely through a variety of networks and is engaging with data users through a Census UK data user working group. NISRA has made efforts to promote and encourage involvement on this working group from UK data users in Northern Ireland.

While the production of UK population estimates is the responsibility of ONS, the user base for these data, and population statistics for Northern Ireland produced by NISRA, may well overlap and future analysis may be affected – for example in NISRA’s latest mid-year population estimates for 2020, comparisons with estimates for the rest of the UK were included. NISRA has a responsibility to inform or signpost its users to relevant information on changes or impacts on data and statistics they use.

Users of statistics in Northern Ireland told us they also have a keen interest in the previously produced Ireland and Northern Ireland publication which pulled together Census 2011 data on the two populations. NISRA and Central Statistics Office (CSO) agreed to work together to produce this again for 2021. However, this output will also be affected as the Government of Ireland decided to postpone the Census of Population of Ireland to 2022. NISRA, along with CSO, continues to plan to produce this output. However, no information on any likely impacts on data quality, given the change in Census date, has been shared with users.

Further steps need to be taken by NISRA to communicate plans and provide more-detailed information, when available, to users of UK population estimates, UK Census data and Ireland-Northern Ireland outputs. As the provision of UK data and statistics is the responsibility of ONS, NISRA should signpost users to related ONS materials on the UK population estimates and UK Census data as this becomes available.

Finding 2

To assure Northern Ireland users of how their data needs will be addressed, NISRA needs to provide users with transparent, accessible and timely information on how UK population estimates for 2021, UK Census data and Ireland-Northern Ireland data will be provided. NISRA should continue to work with, and align communications with, ONS, NRS and CSO to explain any impacts on data quality and describe where user needs may or may not be met as a result.

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Enhancing confidence in the data and processes

Census data collection

NISRA has worked hard and shown a real commitment in its efforts to run live Census collection operations smoothly. The Census team in NISRA is quite small, in comparison to ONS, and it had to reallocate people and manage resources effectively. It had to modify various systems and services for Census, from address checking to the production of adverts and videos for its marketing and advertising campaign.

The recruitment, training and activities of its field staff were greatly impacted during this time and NISRA had to adapt its processes to respond to this, for example moving to online recruitment and training. NISRA engaged with the Chief Medical Officer in Northern Ireland on its plans for Census field operations and took steps to ensure restrictions and social distancing measures were adhered to, including providing appropriate equipment and adapting doorstep routines for the safety of Census field staff and the general public.

NISRA has successfully carried out live operations for the 2021 Census in Northern Ireland and, as stated in this press release on 25 May 2021, a return rate from occupied households in Northern Ireland of over 97 percent was achieved, higher than the 2011 equivalent Census return rate of 94 percent. NISRA told us, around 80 percent of people chose to use the online form to fill in their Census rather than use a paper questionnaire. This was higher than was predicted and NISRA considers that this reflects a successful exercise to promote the Census in Northern Ireland.

NISRA has completed its Census Coverage Survey (CCS) – an independent survey carried out after main Census collection to identify over and under-coverage. NISRA told us its CCS was successfully completed, achieving return rates higher than achieved for the 2011 Census CCS. NISRA will also complete a Census Quality Survey (CQS). The CQS is a separate survey which asks the same questions asked in Census to assess how accurately Census questionnaires have been completed.

Assuring data quality and use of administrative data

With the majority of its collection phase completed, NISRA’s attention now focuses on the processing and estimation of Census data. This will include data cleansing, edit and imputation, and coverage estimation and adjustment. Quality assurance will be part of each stage of NISRA’s data processing and NISRA published its Quality Assurance Strategy in January 2021. This strategy document describes the end-to-end journey of assuring the quality of data through question development, data processing and outputs production. This strategy document should provide users with assurance of NISRA’s commitment to quality and quality management.

NISRA is using a variety of administrative data as part of the 2021 Census. For example, it plans to use an enhanced version of the Census Under Enumeration (CUE) project that was successfully implemented in Census 2011. The method uses administrative data to supply demographic information on households that field staff have indicated did not take part in the Census. The dual approach of the CCS and the ability to scale up the extent of CUE was originally developed as a contingency in the event of a lower than expected response rate.

NISRA has clearly explained its reasoning behind removing the Veterans Question, with the intention to use Ministry of Defence (MoD) data to collect information on veterans. NISRA has worked well with MoD to secure access to the Service Leavers Database and is working towards providing “census-type” information on veterans through secure data linkage. The topic report on the Veterans question explores the research that NISRA undertook to investigate the feasibility of asking a question on veterans in the Census. In this report, NISRA explores the strengths and limitations of the Service Leavers Database and states that it is committed to work with MoD to improve the quality and robustness of these data.

However, information on the range of NISRA’s use of administrative data in the public domain is limited. More information on data sources used in the Census, and NISRA’s judgement of the quality and appropriateness of use of these sources, should be made available alongside Census outputs in order to assure users about the quality of the data.

Developing Census methods

How NISRA takes forward the processing of Census data is determined by the decisions it has made on various different methods. NISRA has told us that while it has modified some of its methods given online data collection, the majority of methods remained largely unchanged from 2011. NISRA has conducted a full rehearsal of the data processing system developed for Census 2021 to assure itself of the appropriate application of methods throughout.

As part of it outputs consultation, NISRA has published some information on its thinking on some Census methods, including an overview of its data processing methods. A Statistical Disclosure Control (SDC) methodology document was published which describes the two SDC methods – the techniques applied to prevent the identification of individuals and households, and their attributes, in published outputs – that NISRA has been considering for the 2021 Census. NISRA has also published an information paper on Statistical output geography which explains why Census output geographies have had to be revised, largely due to the 2015 revision of local government boundaries where a new set of Local Government Districts and Electoral Wards was introduced.

While these papers are available to users as supporting documents for the outputs consultation, these are not easily accessible on the main NISRA Census webpages. There is no methods section on the Census webpages and no detailed information available to users on how methods have been developed or NISRA’s decisions on what methods are being applied.

NISRA has set up a dedicated team to oversee and gain a fuller understanding of Census data as it progresses its work to process and assure the quality of the data. The insights gained will help inform users about quality, strengths and limitations and what they can and cannot do with the data, all of which supports the appropriate use of the statistics. This will be particularly important for 2021 Census data when it comes to areas of change, for example on data particularly impacted by COVID-19 or for new Census questions. NISRA has a responsibility to support and assure users of the quality of Census data and its plans to deliver this alongside Census outputs.

To assure data users of the value and quality of Census data, NISRA should ensure its plans to provide information on quality – including information on data collection and processing, quality assurance activities and quality measures, methods and use of administrative data, and NISRA’s judgement on appropriate use of Census data – are delivered.

Finding 3

NISRA should ensure finalised documentation on quality, information and judgements on suitable data sources, and methods and their application are complete. All supporting information should be sufficiently open and easily available to Census data users alongside its range of Census outputs.

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Responding to user needs

User engagement opportunities

NISRA engages with users through a couple of key routes. As part of the development of its Census planning, NISRA has held formal user consultations, such as its Outputs strategy consultation in 2018 and Topic consultation in 2015. NISRA also has an expert user group, its Demographic Statistics Advisory Group that it consults regularly. The papers and minutes of the meetings are made available in the public domain although NISRA could publish them on its webpages in a more timely manner. NISRA has also held user events at various points over recent years. During our user engagement as part of this assessment, users told us that the NISRA Census team has been knowledgeable, open and helpful.

We have found, however, that NISRA’s approach to public engagement, when it comes to data and statistics, is not as apparent or well reflected on its webpages. Being transparent about how NISRA approaches public engagement gives users confidence in its processes and in how it is open to dialogue and engagement with users. For example, engagement activities – both past and present – and routes for users to engage are not visible on NISRA’s Census webpages.

NISRA’s use of social media around Census day and live collection operations was strong and, more recently, NISRA has made greater use of social media to promote and alert users of its plans for Census data and statistics. This should hopefully allow broader engagement from Census data users.

NISRA’s public engagement strategy during the Census collection period involved communications with stakeholders – including public bodies and community and voluntary sector organisations – through email networks to share, and encourage onward sharing, of key information and messaging to raise awareness and promote the importance of Census. At this time NISRA also held around 80 virtual information sessions with stakeholders. These stakeholder networks, established to support Census collection operations, will now be used to promote its outputs consultation and to communicate important information on Census in the future.

NISRA’s outputs consultation will run until 26 November 2021 and will be an extremely important exercise in understanding user views and their data needs. NISRA ran a consultation event on 3 November 2021 to accompany and encourage responses to the consultation exercise. NISRA has also told us of its plans for events tailored for different user groups, for example a joint event with MoD is planned to engage with users with an interest in veteran data.

With such a wide and varied set of users of Census data, NISRA needs to engage with user groups with different requirements and interests. This includes special interest groups or those from a topic focussed perspective or when, for example, considering the needs of users with different levels of expertise or accessibility requirements.

Finding 4

In order to ensure the relevance of data and statistics to users, NISRA needs to continue to develop and enhance its user engagement activities, connecting with a broad range of users and embracing challenge. NISRA should continually review and seek to implement improvements in its engagement strategies and should ensure its decision making is open and transparent, being clear where users’ needs can or cannot be met.

Communicating plans for census outputs

Throughout our user engagement in both phases of the assessment, there has been strong interest from users to understand what and when Census data will be available to them. Users told us that they need clarity and transparency on the release schedule, as well as the outputs catalogue, so that they can plan their own outputs or broader work accordingly. While we understand that some of this information will be dependent on the outcomes of its outputs consultations, we recognise the demand for this information to support those who intend to use Census data. NISRA intends to publish its outputs prospectus and more detail on the planned release schedule by the end of January 2022.

Up until the launch of its outputs consultation, NISRA had been vague about when its first outputs will be delivered, stating only that it aims for these to be produced by summer 2022. It has been helpful that a clearer proposal on the release schedule has been made available to users – with the aim of a first release of Census Population and Household estimates by July 2022, and all other planned releases being published by summer 2023.

NISRA is committed to producing Census outputs that meet users’ needs and that are timely, accessible and flexible. Producing timely and accurate data from the Census is vital to ensuring high public value.

Finding 5

NISRA needs to deliver its aims in relation to timely, accessible and flexible Census outputs – while ensuring sufficient data quality and supporting appropriate use of the data. It should clearly communicate its plans and timelines for outputs at the earliest opportunity, updating and revising these as soon as more detail is available or to reflect any changes to its plans.

Keeping the general public and users informed

During the operational phase of Census 2021, NISRA delivered a wide-reaching marketing and advertising campaign, utilising traditional and social media routes to promote and encourage public engagement with Census. In a recent report published by NISRA, Public Awareness of and Trust in Official Statistics, Northern Ireland 2020, it was encouraging to note that many respondents, whether they had heard of NISRA previously or not, were aware of Northern Ireland Census statistics.

Since the main Census collection period, NISRA has continued to use social media to engage with the broader public and users of Census data and statistics. Recognising and thanking the general public for their important contribution in providing personal data to NISRA for Census and assuring them how their data is being securely handled and how it will be used, should be an ongoing feature of NISRA planned communications. NISRA has made significant investment in its communication and engagement and plans to continue these efforts with the focus now moving to Census outputs.

Over the course of this assessment NISRA has made improvements to its Census webpages and while these webpages are relatively easy to navigate, the content for users of Census data is limited. In addition, some of the tools used to communicate progress and future plans through the website, such as the Census Milestones webpages, have not been consistently kept up to date, although we recognise these have been recently refreshed.

Having accessible and easily findable information supports the appropriate use of data and statistics.

Finding 6

To best support Census data users, NISRA needs to continue to improve its webpage navigation for current materials. NISRA’s plans for a separate website or webpages for Census outputs themselves will require sufficient consideration of its navigation and accessibility. NISRA should keep webpages and content refreshed and current.

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A continuous improvement approach to Census

Innovation and improvement in Census outputs

NISRA plans to disseminate its Census outputs through two main routes, pre-defined tables – which will be similar to the key statistics and quick statistics tables produced for the 2011 Census – and through the use of an interactive flexible table builder. For both of these dissemination routes, NISRA has worked collaboratively to introduce new, more flexible solutions to benefit its Census data users. The pre-defined tables will be available through a new data dissemination system, PxStat, which was developed by CSO and used as its open data portal. It will allow users to filter using variables in the tables or by geographic area to tailor the data and statistics to their needs. This new system is planned to be used across NISRA’s statistical outputs, with Census as the first data to be made available through this route.

NISRA will produce fewer pre-defined tables for 2021 as users will have the additional facility to create their own tables using the proposed flexible table builder. This tool should allow multivariate tables to be created and include all standard topics at Local Government District level. Developed by ONS, the table builder will automatically apply statistical disclosure control to the tailored user outputs using cell key perturbation methodology. Using a tool developed by ONS brings benefits and efficiencies, including that users accessing data through these routes will have a common user experience and should gain familiarity with the new table builder system.

Both these developments should increase the accessibility and flexibility of Census data for users and, while these new tools are still in development, NISRA has shown its commitment to implement new technologies to enhance the presentation and disseminations of Census outputs. At the outputs consultation event in November, it was positive to see NISRA demonstrate its new flexible dissemination tools which will be available for users of Census 2021 data.

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