A. Information on data sources
A. ONS should publish details of which data sources it intends to use for the administrative data-based migration estimates (ABME) (strategic) and provisional state space model (tactical) approaches. It should also set out how each additional source impacts the migration estimates and the implications for how users should interpret the different provisional and updated (previously referred to as final) estimates.
Actions taken and commitments made by ONS to meet the recommendation
ONS is no longer using the state space modelling approach. At the moment, it is using three main data sources to produce migration estimates for different groups of migrants:
- Home Office Borders and Immigration (HOBI) data for non-EU nationals
- Department for Work and Pensions’ Registration and Population Interaction Database (RAPID) for EU nationals; and
- the International Passenger Survey (IPS) for British Nationals.
ONS has published information about the key data sources alongside estimates and provided users with links to Home Office data user guides. ONS is exploring implementing HOBI data into long-term international migration estimates (LTIM) instead of the Department for Work and Pensions’ RAPID data to estimate EU citizen migrants in 2024. ONS published International migration research, progress update: November 2023 which informs users about the future implementation of HOBI data for estimating EU citizen migration. This publication also informs users that this work is ongoing, and a further update will be published next year.
ONS has published a range of documents telling users about data sources, including Long-term international migration: quality assuring administrative data which informs users about ONS’s quality assurance of administrative data processes. ONS also signposts users to Home Office data user guides for information on the HOBI data.
The IPS arrivals data source used to measure British National migrants will cease in Spring 2024. ONS is still researching alternative data sources for estimating the number of British Nationals migrating in and out of the UK. ONS provided an update for users in the research update published in November and plan to provide a further update in May 2024.
ONS has a revisions policy for population and international migration statistics. This policy is clearly signposted from the LTIM bulletin to support users understanding of the differences between provisional and updated LTIM estimates.
OSR’s evaluation of evidence
Even though ONS is changing its approach to producing these statistics, the principles of openness around the use of data sources still need to be followed. ONS has now published information on data sources, particularly on quality assurance, ongoing developments and future plans to support use of the estimates.
ONS should keep users informed about the progress of its research into alternative methods for measuring British National migrants as it develops them, to build user confidence in the future of migration estimates.
ONS’s revision policy supports users’ understanding of how ONS revises estimates. This was clearly signposted from the LTIM bulletin, ensuring that this information is easily accessible for users. This further develops public understanding and confidence in the estimates.
We welcome the progress ONS has made against this recommendation and expect ONS to continue its approach throughout the transformation.