1. About our transformation

This page provides an overview of our transformation of population and migration statistics to put administrative data at the core of what we do. This includes an update on our latest progress alongside links to all our related research reports. Your feedback on our latest update would be valuable.

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2. Our latest updates

Today (14 February 2020) we have published a series of articles exploring the concepts and definitions that underpin the measurement of international migration and how they can be applied within administrative data. This area of research is an important element of our transformation framework and our aim at this stage is to set out how these definitions are used currently, summarise our latest research with administrative data, and gather feedback from users to inform next steps.

Defining and measuring international migration

This article provides an overview of our research into how we define and measure migration and why this is an important topic given increasingly complex migration patterns and the need for further flexibility in order to reflect population changes in a modern world. It also sets out the concepts, definitions and data sources that are currently used and provides a summary of the different approaches used in other countries.

Exploring international migration concepts and definitions with Home Office administrative data

Administrative data provides us with alternative sources of information on international migration and an opportunity to explore different ways to define and measure it. In this article we have investigated how we can use one such source, Home Office Exit Checks data, to apply the current UN definition of a long-term international migrant, as well as exploring two potential supplementary definitions. This work has helped us develop our understanding of international migration and shown the potential for using definitions based on a range of administrative data sources in future.

Understanding non-EU student migration

As study is one of the two most common reasons for people to move to the UK, there has been a growing importance placed on understanding student travel patterns and what administrative data can tell us about this topic. This article presents research using Higher Education Statistics Agency (HESA) student records linked to Home Office Exit Checks data to investigate the patterns and length of student presence in the country.

Applying a quality framework to longitudinally linked administrative data

We have developed a quality framework to assess statistical error in administrative data sources and applied it to longitudinally linked Home Office Exit Checks data. This has further deepened our understanding of this data source and the findings from this research will inform statistical design decisions and future linkage of multiple administrative data sources.

Next steps and other research

This work forms part of our longer-term research to transform population and migration statistics, which we will continue to work on collaboratively with partners across government, including the devolved administrations in Northern Ireland, Scotland and Wales.

In addition to the research published today (14 February 2020), we are also undertaking ongoing research into circular travel patterns among international migrants, following previous user feedback that highlighted the need to develop a better understanding of this population group. Our next steps include the use of a longer time series of Home Office Exit Checks data to enable us to explore this topic further.

The series of articles described here include some proposed next steps for our research into migration concepts and definitions. However, we would like user feedback at this stage to help inform the future direction of our work and have included a range of questions in these articles that we are particularly interested in getting your views on.

If you would like to get in touch, please contact us by email at pop.info@ons.gov.uk.

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3. Our mission – why transform?

It is our mission to provide the best insights on population and migration using a range of new and existing data sources to meet the needs of our users. This is increasingly important in a rapidly changing policy context, where we know our users need better evidence to support decision-making at both national and local levels.

As set out in our previous work on the Administrative Data Census project, the current population system is heavily reliant on the decennial census. While this provides granular data at the lowest levels of geography every 10 years, it delivers less detail throughout the interim years. Additionally, the quality of our population estimates declines as we move further away from the census year.

We have also long acknowledged that the International Passenger Survey (IPS), which underpins our existing international migration estimates, has been stretched beyond its original purpose and that we need to consider all available sources to fully understand international migration.

Enabled by data-sharing powers in the Digital Economy Act 2017 and guided by our data security principles, we are therefore seizing the opportunity to make use of more data to give us a much richer understanding of how our population is changing.

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4. Why are these statistics so important?

Population and migration statistics underpin a wide variety of other statistics (such as unemployment rates), support a vast range of decisions and inform public debate. For example, the ability to forecast pensions, make decisions about local services (such as the number of school places or the provision of health services for an ageing population) and decisions about where to site new businesses.

In a rapidly changing policy context, we also know that our users are highly interested in how migration patterns are changing and what this means for society and the economy. For example, the contribution and impact that migration has on public services – such as education, healthcare – and on the UK labour market. This includes both the national picture but also what is happening at a more detailed regional and local level.

It is therefore essential that our population and migration statistics are robust, timely and meet this broad range of user needs.

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5. How are we transforming population and migration statistics?

Working in partnership across the Government Statistical Service (GSS), we are putting administrative data at the core of our population and migration statistics.

Using our data-sharing powers through the Digital Economy Act 2017, we have been progressing research into how we can link a range of government data sources to build an integrated system for measuring population and migration.

In January 2019, we published a research engagement report that updated users on our ambition for putting administrative data at the core of our statistics by 2020, dependent on acquiring access to the further data sources needed to fill gaps in coverage.

Since January 2019, we have made further progress towards our ambition. For population statistics, this includes our June 2019 update on developing administrative data-based population estimates (ABPEs), where our latest rules show promise for removing patterns of over-coverage seen in previous research. For migration statistics, this includes our improvements based on a preliminary adjustment using administrative data from the Home Office and the Department for Work and Pensions and our move to reclassify these statistics as Experimental Statistics to support ongoing development and innovation.

Whilst we continue to make progress in embedding more administrative data in our statistics, we know there is more we need to do to put administrative data at the core of these. Access to data continues to be one of our main challenges and we do not yet have all the sources we need to deliver a fully integrated administrative data-based statistics system. These are needed to fill important gaps in coverage for groups such as EU migrants, where our available data sources are more limited.

We are continuing to make important steps in addressing gaps in coverage – for example, collaborating with the Home Office and the Department for Work and Pensions to explore how further data could support us in measuring EU migration and improving our adjustment method. However, there are a range of factors we need to take into account and we are committed to meeting high standards in the data we use and how we incorporate that data in producing official statistics.

Data security is paramount. As we harness the power of an increasing volume and variety of data, we must ensure that we continue to protect and secure this appropriately. We are therefore continuing to work in close partnership across the Government Statistical Service (GSS) to ensure we apply appropriate safeguards and have an agreed approach to how we manage and share data.

Data quality is also crucial to the success of our transformation work. Once we have acquired further administrative data sources, we also need time to fully understand their strengths and limitations and assess the best way to integrate them into our statistics system. Our move to reclassify migration statistics as Experimental Statistics supports this process, by clearly signalling to our users how we are developing and evaluating our data sources and methods.

Our transformation journey

Our ambition – as set out in our January 2019 report – has been to put administrative data at the core of both population and migration statistics in 2020. However, based on our latest progress on data access, we have revised our plans to focus on the priority areas where we can best address user needs in the short-term, continuing to embed more administrative data as this becomes available and as our research progresses.

In 2020, we now plan to focus on delivering improved migration statistics by refining our preliminary adjustment methodology. We will then build on this – alongside continuing our admin-based population estimates (ABPE) development – to deliver improvements to population statistics from 2021 instead. This in turn will support the delivery of the best quality census outputs in 2022 and the delivery of a fully transformed population and migration statistics system based on integrated administrative data by 2023.

A summary of the milestones on our transformation journey are set out in the following table.

This transformation journey – alongside the work to transform surveys across the Office for National Statistics (ONS) – also supports the ambition that “censuses after 2021 will be conducted using other sources of data” and importantly that the outputs we publish should be coherent and meet the needs of our users. This is essential to providing evidence to inform the recommendation to the UK government in 2023 about the future of population and housing censuses in England and Wales.

We have taken the decision not to benchmark the administrative data census outputs with the outputs from the 2021 Census. Instead, we will ensure that we use the best available sources to produce the best-possible outputs from the census – using our understanding of the differences between administrative data and the census, and the strengths of all data sources. We will iteratively develop our transformed population and migration statistics system, taking on board feedback from users and making the best use of new data and new methods as they become available. We will rigorously quality assure new methods and share the impact of any changes made, demonstrating the benefits and improvements before implementing them.

Alongside supporting the decision on the future of the census, our transformation journey also plays an important role in supporting our progress in measuring the global Sustainable Development Goal (SDG) indicators in the UK. Migratory status is one of the standard disaggregations required by the United Nations to measure and report on the global SDGs and our transformation work will help to improve the evidence base by providing more granular data in future.

What is happening in the next year?

To keep users of population and migration statistics updated on our progress towards these milestones, we plan to publish regular updates over the next year.

The following table summarises our upcoming publications and focuses on migration statistics given our aim to deliver further improvements to these in 2020. We plan to make these improvements when we are confident that it is the right time to do so, based on the best available data and taking on board feedback from our users. This includes extending our current EU adjustment (which applies up to 2016) as soon as possible, as user feedback shows this is a priority. However, we need to bring in further data to do this and so we are working across the Government Statistical Service (including with the Home Office and the Department for Work and Pensions) to assess what sources will be available to help us refine our methods.

Throughout the year, we will continue to work closely with the Office for Statistics Regulation (OSR) to update them on our progress and to review when we will reapply for National Statistics status for ONS international migration statistics.

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6. What have our users told us?

Our users sit at the heart of our framework for transforming these statistics (Figure 1), which describes the important questions we need to answer to meet their needs.

To meet our users’ needs we need to provide coherent statistics on the size (or stock) of the population and how it changes over time (flows, both nationally and locally). We also need to tell a clear story about what is contributing to this change and show how different groups in the population impact on society and the economy, including on our workforce, communities and public services such as the NHS and schools. This needs to be recognised as the story that is being experienced by our users.

Our users have also told us that they want us to deliver these statistics frequently and in a timely manner to be able to make evidence-based decisions. Our statistics also need to be relevant in a rapidly changing society, and we need to be able to report on their quality.

Feedback gathered shows support for how we are reviewing current data sources and looking to maximise the value of administrative data in future, whilst challenging us to provide more evidence to ensure we instil confidence in these statistics.

To make sure that our transformation journey continues to be as open and transparent as possible, we will:

  • regularly publish research and methods as we develop them
  • continue to present analysis showing the coherence between different sources of information
  • engage with our users and stakeholders, seeking regular feedback
  • use our research findings, the best available data and methods, and the feedback from users to make decisions about which improvements to make each year
  • implement changes to our statistics when and where appropriate, clearly communicating these changes to users in advance of making them

How can users get in touch?

We welcome your feedback on this update and on our transformation journey. If you would like to get in touch, please contact us by email at pop.info@ons.gov.uk.

We have recently presented our research at the 2019 Royal Statistical Society Conference, the British Society for Population Studies Conference, the Migration Statistics User Forum and the International Conference on Administrative Data Research.

We are also working with local authorities, experts from academia and other government departments through invited engagement groups to help shape and quality-assure our work. Additionally we are engaging with other national statistical institutes (NSIs) across the UK and internationally to share experiences and seek feedback on our plans.

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7. More about our transformation journey

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8. More about our official population and migration statistics

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Contact details for this Article

Ann Blake
Telephone: +44 (0)1329 444661

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