National Statistical

We are launching a new phase of work towards developing harmonised standards for sex and gender identity data collection. Here Emma Rourke reflects on our work so far, the best practice approach we will implement and our plans for the coming months.

Data on sex and gender identity are important when understanding our society. Both statistical producers and data users have told us that they value a harmonised approach to both characteristics which allows people to effectively and accurately compare data that has been collected across different datasets.

Today we’ve set out the Government Statistical Service (GSS) plans to review and update harmonised standards and guidance for the collection of sex and gender identity data, including further question development and testing. This will take account of survey and administrative data frameworks, to build confidence in future guidance and the use of such data.

The first collection of gender identity and trans status data via censuses in England, Wales and Scotland generated valuable insights about the strengths and limitations of collecting data on the topic. To reflect new evidence and our evolving understanding of how to collect this data, in September we requested a change to the designation of Census 2021 gender identity statistics for England and Wales from accredited official statistics to official statistics in development, as explained here.

We also recognised, along with the Office of Statistics Regulation (OSR), that further support is needed for producers considering how to collect data on gender identity. I’ve today written to the OSR, providing an update of what we have done and outlining our plans for the coming months.

The GSS harmonisation team, based in the ONS, will be working to provide advice on harmonised standards, developing questions and guidance to support consistency, coherence and comparability of statistics.

ONS analysts are also conducting new work to provide more detailed information on the uncertainty associated with the Census 2021 gender identity estimates, and guidance on their appropriate use. This work is considering a variety of approaches to identifying and communicating uncertainty and will provide use cases with recommendations for appropriate use and limitations in different scenarios. It will also bring together learning from Census 2021 in England and Wales and from Scotland’s Census 2022 where a question asking trans status or history was used.

Interim guidance

While all of this work is being carried out, we’ve created an interim guidance page for producers of statistics and researchers who are currently using, or thinking about including, a gender identity question on their surveys or in their administrative data collection. It will continue to be updated as further ONS research is published on sub-national and other smaller group breakdowns of the census data.

This guidance sets out the gender identity questions used in censuses across the UK, alongside additional information and considerations users should take when considering how to ask about this topic in your data collection.

There is no agreed best practice for collecting gender identity data yet. The most recent way of collecting data in England and Wales was through Census 2021.  Scotland’s Census 2022 asked a question on trans status and history. Some differences in the data collected by each method are expected, reflecting different question wordings. However, these sources provided broadly consistent estimates at a national level.

If you are looking to include a question on gender identity or trans status in your data collection, where possible, we would recommend waiting for our work to develop new harmonised standards to conclude.

However, if you are unable to wait for this work to be completed and have a clear need to collect this data, we have outlined some consideration users should take. Meanwhile, the OSR has also provided guidance in applying the principles of the Code of Practice for Statistics when making decisions about the collection and reporting of statistics and data about sex and gender identity.

Future work

The UK Statistics Authority (UKSA) has the statutory objective of promoting and safeguarding the production and publication of official statistics that serve the public good.  As part of the UKSA, the ONS has a responsibility to uphold that objective. As such it is important that we listen to all voices, including statistical producers, data users, future survey participants and others.

During 2025 we will therefore share our findings from quality analysis of the Census 2021 gender identity estimates. We will hold a series of regional events to listen to stakeholder needs for questions and future data on the topics of sex and gender identity. We will also conduct further research into how respondents conceptualise these topics, including how these concepts vary for different populations.

We’re also going to carry out further testing with the wording used for the England and Wales census in 2021 and Scotland’s census in 2022 to understand the respondent experience for different populations. As part of this process, we will also consider wording from other countries on the topic. Following this, we will develop prototype questions for iterative testing, based on evidence gathered during previous phases.

Our aim is for the final standards to take into account a range of views and to have been rigorously tested. It is worth noting that being harmonised is about aligning with others, not necessarily being identical to them. As such, some of our harmonised standards can be tailored for specific situations. And in some circumstances, where it is not appropriate to suggest harmonised questions and definitions, guidance explains the topic landscape to help users understand where they can and cannot compare data. We intend to publish our research findings for the development of updated sex and gender identity harmonised standards for the online mode in autumn 2026. We recommend statistics producers review this guidance information once it is published.

Setting the standards

The UK Statistics Authority’s Inclusive Data Taskforce published eight recommendations to ensure that data and evidence across the UK is reflective and inclusive of all so that ‘everyone in society counts and is counted, and no one is left behind’. ONS will be guided by all these recommendations during our work. The work of our GSS Harmonisation Team is one way in which we address the need to capture better data for all groups across areas of life in the UK, and ensures regular review of the standards of data collection in line with changing social norms and respondent and user needs.

Our work also includes a commitment to:

• Create an environment of trust and trustworthiness which allows and encourages everyone to count and be counted in UK data and evidence.
• Take a whole system approach, working in partnership with others to improve the inclusiveness of UK data and evidence.
• Ensure appropriateness and clarity over the concepts being measured across all data collected.
• Ensure UK data and evidence are equally accessible to all, while protecting the identity and confidentiality of those sharing their data.

We welcome people expressing interest in being involved with our work on sex and gender identity statistics. If you want to receive information about the regional events in 2025, or to share feedback and views please contact outreach.engagement.community@ons.gov.uk