From Mary Gregory, Executive Director, Population, Census and Social Statistics, Office for National Statistics
To: Ed Humpherson, Director General, Office for Statistics Regulation
Dear Ed,
Mid-year population estimates for England and Wales
I am writing to you today to acknowledge the mid-year population estimates (MYE) compliance review report you published in May. We would like to thank you for your engagement with my teams during this process and for the findings of the review. The report confirmed that the continued accreditation of these statistics is conditional on ONS meeting four requirements before or at the same time as the next publication of the MYEs, in summer 2026.
We have today published the mid-2025 population estimates for England and Wales, which include revisions to mid-2022, mid-2023 and mid-2024 estimates to incorporate the improved long-term international migration estimates. We have also published a blog and a suite of supporting information to help users of population estimates understand the quality of the estimates and what this means for how they can be used. In delivering this work, we have tried to take a comprehensive and user-focused approach to addressing the requirements in the compliance review, while improving the overall experience for users of the estimates.
The publication of MYEs includes a statistical bulletin which contains clearer and more prominent information about the uncertainty around the estimates and guidance on how the estimates can and cannot be used. Alongside the publication we have also published additional articles - linked below - which provide detailed information on the strengths and limitations of the MYEs, to aid users’ confidence in them and increase understanding of how they can be used appropriately. The article about the effect of the coronavirus pandemic on data and quality of population estimates outlines the effect the pandemic had on different components of the MYEs and how these have been managed. The publication of the MYEs contains the following components:
- Mid-2025 population estimates for England and Wales
- Quality and methods guide
- Population Statistics and Sources Guide
- Quality overview of data sources used in mid-2025 MYE for England and Wales
- Improving population estimates for England and Wales
- Local authority quality of population estimates for England and Wales
- Effect of the coronavirus pandemic on data and quality of population estimates for England and Wales
- Subnational long-term international migration methodology
The article about improving population estimates covers the areas we will focus on over the next two years: data sourcing, supply and quality, as well as dissemination of outputs and user engagement. In particular, our work to improve the methods and data used for producing subnational estimates of international migration and estimates of internal migration will be central to the improvements to MYEs. Our aim is to ensure we have a coherent system for producing population statistics which supports user confidence. The work identified in this plan will also help us continue to progress the recommendations outlined in the MYE compliance review.
We will continue to work closely with local authorities and other users of population estimates to better understand local population change and the challenges associated with measuring it. This collaboration will help us improve the quality of the estimates, reduce uncertainty over time, and provide greater confidence in areas where population change is more complex, including those with large student populations, high migration and mobile working-age populations.
We will publish updates on progress within the population and migration quarterly update, along with providing an additional layer of assurance by providing an update to the Population Statistics System Committee every six months. We will also continue to deliver improvements to our critical outputs in the near term through a Population Statistics System Plan to be published later in 2026. We welcome your continued engagement as this work progresses.
Yours sincerely,
Mary Gregory