Dear Jen

Review of 2021 England and Wales Census data on Gender Identity: Interim report

In my letter to you in April 2023, I shared the emerging findings from our review of statistics on gender identity based on data collected as part of the 2021 England and Wales Census. The review considers ONS’s approach to responding to questions raised by users about the results of the gender identity data[1].

As you know, ONS initiated a research programme into these statistics after some users raised concerns regarding the estimates of the transgender population in the first release of these statistics. The results were planned for publication during Summer 2023, but on 30 August, you confirmed the research into these data is ongoing and that ONS will publish further updates in due course.

In light of this update, we have today published an interim report. This sets out our expectations of what is needed from ONS to provide assurance on the gender identity data in line with the Code. We have based these on what we know so far about how ONS tested, quality assured, communicated and engaged with users, both in advance of publishing the results and where appropriate from the research to date.

As the interim report makes clear, there was always good reason to expect a significant degree of uncertainty around estimates of the transgender population derived from the gender identity question in the 2021 Census, given that this is the first time that the question has been asked, that declaring their gender identity will have been a sensitive personal matter for some respondents, that the concept of gender identity may be unfamiliar to many people, that the proportion of the population who are trans is relatively small and that there are few robust alternative sources of data to cross-check against.

Under these circumstances, user interrogation of and feedback on the published data would be expected to provide a useful additional layer of quality assurance. A willingness on the part of ONS to provide further context and clarity on the initial estimates would be evidence of the strength of the Census process and not a weakness. ONS providing updates to the interpretation of these estimates should be regarded as a normal part of ongoing statistical production for a new area of data collection. The same would be true of any changes to the initial estimates, as long as they are fully and transparently explained. Such updates should not undermine user confidence in the robustness of the Census results as a whole, in which most questions have been asked many times before.

The interim report sets a range of recommendations for ONS to address to provide assurance on the gender identity data in line with the Code of Practice for Statistics. In particular the report recommends:

  • ONS should publish a statement within four weeks of this interim report that sets out a timeline for its ongoing research, covering what it is analysing and what it plans to publish by when.
  • ONS should make data available to understand subgroups of the reported transgender population.
  • ONS should consider any potential misunderstanding of the question or mode effects on the data as part of its analysis into the agreement rates for the gender identity question in the Census and Census Quality Survey. In particular, it should publish analysis of group differences to inform future use of the data and question.
  • As part of the ongoing development of the harmonised standard for gender identity, should the question remain the same, ONS should carry out further testing of the question.

We will publish a follow up report with our findings after we have reviewed, and engaged with users on, the full set of research outputs.

Please do not hesitate to get in touch if you would like to discuss any aspects of this letter and accompanying interim report.

Yours sincerely

Ed Humpherson
Director General for Regulation

[1] The ONS’s first release of statistics on gender identity based on Census data was in January 2023. When publishing the results ONS said: “Gender identity refers to a person’s sense of their own gender, whether male, female or another category such as non-binary. This may or may not be the same as their sex registered at birth.”