Population and migration statistics system transformation – recent updates

In our previous update we described how we have responded to the challenges in measuring population and migration during the coronavirus (COVID-19) pandemic. There have been disruptions to the methods in how we collect statistics, including the suspension of the International Passenger Survey (IPS), the core source for previously measuring international migration.

In response to these challenges, we have accelerated our work on producing population and migration statistics using administrative data. We published our initial research in April 2021 in Admin-Based Migration Estimates using Department for Work and Pensions (DWP) Registration and Population Interaction Database (RAPID) and Home Office visas and border data. This informed users of our approach for transforming migration statistics for the future but was not timely and so did not show the impact the pandemic was having on migration.

To meet the demand for more timely and granular statistics, we also published innovative estimates of international migration using statistical modelling techniques, which estimated migration during the first four months of the pandemic (March 2020 to June 2020). This enabled us to publish an early indicator of the overall population, to June 2020.

In May 2021, we published methodology on how we can use HM Revenue and Customs (HMRC) "Real Time Information (RTI)" data to reweight the Labour Force Survey by country of birth to help to address a non-response bias introduced by changes to the survey collection, a result of the coronavirus pandemic. This work followed recent experimental analysis using the RTI data to explore how the labour market is changing, and what insights this can give us about the UK population.

In June 2021, we published our official population estimates for the UK to June 2020. This was our first official estimate of the UK population since the pandemic began and provided estimates of the population by age and sex by each local authority. Built forwards from the 2011 Census, and before 2021 Census results are published, the challenge in producing the best possible estimates is at its greatest.

Since then, working in collaboration with Home Office and DWP, we have developed our thinking in how these sources can provide even further insight into changes in the population and migration, including more timely measures.

We are sharing our plans for the future of population and migration statistics below. In addition, we have published our plans for upcoming population and household projections.

As part of the release of official population estimates for the UK to June 2020, we have also set out what the experimental estimates are for international migration for the same period. They make use of estimates from the International Passenger Survey to February 2020 and modelled migration estimates from March to June 2020. The estimates largely reflect what were used in our early population indicators but there are some differences explained in the methodology paper as part of our official population estimates release.

Recent engagement with users and experts has helped steer the future development of migration statistics. Our work is a collaborative effort across government, both in terms of data and analysis.

There continues to be a need for migration estimates to feed into an overall population statistics system. Feedback has encouraged and challenged us to look beyond replicating what we’ve published historically and exploit the opportunities administrative data sources can provide.

Our Admin-Based Migration Estimates (ABMEs) report highlighted how migration statistics could be produced using administrative data. The method is based on actual behaviours, which means waiting before a person has moved to the UK or left the UK for at least 12 months. Therefore, there will be time lags before we could use these sources in isolation. We have also identified gaps that are harder to measure, such as students, children and UK citizens.

Going forward, the future development of ABMEs will be supported by statistical modelling. This will build on the development of our previous modelling research published in April 2021 and our ABMEs research, with a greater focus on the use of Registration and Population Interaction Database (RAPID) data. This will make these statistics timelier and improve coverage. ABMEs will also allow insightful analysis on subpopulations of migrants, including migrant workers, students and families and dependents.

Bringing this all together our future outputs are expected to be:

• Autumn 2021, Population of the UK by country of birth and nationality: year ending December 2020. This is subject to progress made on reweighting the Labour Force Survey.

• Autumn 2021, our research plans and progress taking into account user feedback and data source strengths.

• Autumn 2021, ABMEs supported by statistical modelling for Quarter 3 (July to Sept) and Quarter 4 (Oct to Dec) of 2020, building on methods used previously.

• Early 2022, ABMEs supported by statistical modelling for Quarter 1 (Jan to Mar) and Quarter 2 (Apr to June) of 2021. Further improvements to modelling methods including the use of more granular administrative information in RAPID and Home Office data.

• Early 2022, a methods paper outlining our approach to ABMEs with statistical modelling and how this feeds into a transformed population system. It will make use of the best sources available as well as initial proposals for a revisions policy.

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