Background

High-quality population and migration statistics paint a detailed picture of our society. They supply local and central government policymakers, public service providers, private sector businesses and voluntary sector organisations with the information they need to make good decisions and deliver services and products effectively. They also help citizens, the media, think tanks and researchers understand how the size and make-up of the population is evolving.  

For more than two centuries, the traditional, questionnaire-based census of the whole population has been one of the critical sources of this information in England and Wales, providing a snapshot of the population every ten years. Originally a straightforward population count, the census has evolved over time, with increasingly sophisticated methods being used and the questions reflecting shifting priorities in our rapidly changing society.

Census 2021 made greater use of administrative data than ever before and was the first to be held primarily online, following a recommendation from the National Statistician in 2014. It achieved a high response rate, with 97% of all households completing the questionnaire, and all local authority areas reached response rates of at least 88%. It also saw a timelier release of data than ever before, with the first results released a year after the data-collection operation, and all major England and Wales releases published by the end of 2023. 

The 2018 white paper, ‘Help Shape Our Future’, included the commitment to present a recommendation to the UK Government on the future of the census, a commitment that the publication of this document fulfils.  

The breadth and depth of administrative data held across Government represents a huge opportunity for the transformation of statistics. Extensive work undertaken by the ONS over the last decade has demonstrated what is possible with these data. This progress demonstrates great promise in the development of official statistics using administrative data. It is the Authority’s view that this work should continue to be resourced over the long term, so that these outputs can reach full maturity, paving the way for a more sustainable and predictable statistical system that takes full advantage of developments in technology and data availability. 

Across the world national statistical institutes are exploring greater use of administrative data as part of their strategy to address challenges around quality, coverage and data availability. Many of these countries rely on the strength generated in combined methods.

The progress made in recent years with administrative-based statistics provides the opportunity to iterate our approach to the design and delivery of a traditional census operation. This will build resilience into the delivery of the census in 2031, drawing strength from different data sources and responding to the risk presented by low response rates to social surveys and recent censuses in other countries since the pandemic. This would combine the efficiencies and opportunities of administrative data with the scale and precision provided by a mandatory questionnaire-based census.

The Government has made clear its commitment to a transformative digital agenda as a key driver of reform in public services, which would be a significant catalyst to realise the full power of administrative data. This commitment will be significant in unblocking the challenges currently experienced with data-sharing and will be critical in the ongoing development of the ONS’s long-term ambition with administrative data.

The wealth of analysis enabled by administrative data is increasing each year and in time, with the right investment, could one day surpass the benefits of a traditional census.

As part of the Census and Data Collection Transformation Programme, the Authority set out the following three evaluation criteria for assessing any potential recommendation: 

1. The ONS’s plans for the future statistical system are supported by users as meeting their core user needs for statistics about the size and composition of the population of England and Wales, its characteristics, and housing stock.
2. This statistical system will be flexible and resilient enough to respond at pace to future and emerging user needs, adapting to changes in available data sources; and will be capable of going beyond core needs. 
3. Methods and approaches are peer-reviewed and compliant with relevant legislative and ethical considerations, and our plans are accepted by the public, with a business case and programme plan in place to deliver a sustainable statistical system. 

To support the development of a recommendation aligned with these criteria, the Authority has considered a range of evidence drawn from the ONS’s research, a public consultation and expert advice. It is ONS’s assessment that users will welcome a questionnaire-based census of the whole population in 2031 and the recommendations made in this document. 

The ONS has published extensive research on its website in consultation with independent experts in methodology, data ethics and inclusivity. It also conducted a public consultation on the future of population and migration statistics, between June and October 2023. Coinciding with the consultation launch, the ONS published a summary of the population and migration statistics transformation research and assessed it against the evaluation criteria.  

The ONS’s Data Strategy aims to realise the full value of data as a strategic asset, while maintaining high levels of trust and transparency. As the ONS works to implement this, linked administrative datasets will play an increasingly important role in the production of its statistics. Given the sensitive nature of the data contained in these datasets, maintaining the trust of the public is crucial.

Following advice from the National Statistician’s Data Ethics Advisory Committee, the ONS has engaged directly with members of the public to explore contemporary attitudes to data and whether these are changing over time. In January 2025, the ONS published a summary of public attitudes to data including views on data linkage and the use of administrative data for statistical purposes. This draws on a range of ONS and external sources between 2014 and 2025. The latest research indicates that the public is broadly accepting of data-sharing and linkage, and that this has consistently been the case over the decade. Furthermore, members of the public increasingly assume that data-sharing and linkage are already widespread practices across government organisations.

The Authority recognises that the ONS must work to maintain high levels of trust. The ONS should retain and strengthen its commitments to maintaining transparency with the public about what data sources are used and how. This includes communicating information on the privacy and security measures in place to maintain trust and protect privacy.