Census 2021: Final guidance for the question “What is your sex?”

The Office for National Statistics (ONS) has conducted a comprehensive programme of research and testing to finalise Census 2021 questions and guidance. Along with the Census 2021 topic consultation, this confirmed the ongoing strength of need for data on sex. We provide a full list of the tests used in the development of the Census 2021 questionnaire in the summary of testing for Census 2021¹. As a result, the ONS recommended:

• the 2011 Census sex question wording and response options should not be changed

• the sex question should state that a question on gender identity will follow

• the response options "Male" and "Female" should be listed in alphabetical order

The research leading to these recommendations is available in Sex and gender identity question development for Census 2021¹.

Details of the guidance used in the 2019 Rehearsal (2019:15), and a summary of the research that informed its development, was published in September 2019 in Guidance for questions on sex, gender identity and sexual orientation for the 2019 Census Rehearsal for the 2021 Census.

In the guidance report we committed to reviewing the "What is your sex?" question guidance following the 2019 Rehearsal. This report describes the results of that review. A report on the additional qualitative testing (2020:6) conducted as part of this work will be published separately.

Notes for: Overview of testing and guidance for Census 2021 sex question

1. References to tests take the form (year:test number). "Year" refers to the calendar year the test was undertaken in and the test number is the position of the test within all testing that took place in that year. For example, the fifth test conducted in 2017 would be referenced as (2017:5).

Following the review of the question guidance we have made three recommendations:

• the target concept of the question "What is your sex?" is sex as recorded on legal/official documents

• those who have physical sex development that is different to what is generally expected of males and females should not be provided with guidance suggesting they could provide this information in the gender identity question

• the guidance wording should be updated to minimise barriers to completion of the census and the sex question

How we came to these recommendations, and the impact on the guidance is described in the rest of this section.

Target concept

The evaluation of the sex question concept was framed around the dimensions of quality in the European Statistical System, looking at:

• Census 2021 data users need: "relevance" and "comparability and coherence"

• impact on Census overall: "accuracy and reliability"

This evaluation was presented to the Methodology Assurance Review Panel in December 2020. The methodology article, Methodology for decision making on the 2021 Census sex question concept and associated guidance, recommended that the concept of sex to be collected in Census 2021 should be "sex as recorded on legal/official documents". This differs from our initial recommendation, based on the 2011 Census guidance, of self-identified sex, although for most respondents the answer would be the same.

The panel felt that the Office for National Statistics (ONS) had clearly set out a range of target variables and its rationale for arriving at this recommendation.

Differences of physical sex development

In the 2019 Rehearsal, the guidance for the gender identity question stated:

"If you would like to record that you have variations of sex characteristics, sometimes also known as intersex, you can use this write-in box. If you would like to, you can also write in your gender (for example: "intersex, non-binary")."

This was included because some stakeholders had stated that this would increase inclusivity of the question. However, more accessible location for this guidance would be in the sex question.

We have conducted further engagement to confirm the benefits of including this guidance. This showed that the guidance was not appropriate as:

• there is no strong and clearly identified user need for collecting this information in Census 2021

• this is a sensitive topic and private for some

• we are asking the person to provide their sex attributes in a gender question and, as such, are conflating concepts

• data collected on this population in this way would be of low quality

This recommendation was taken to the National Statistician's Data Ethics Advisory Committee for review. The Committee agreed with our assessment and the recommendation that this guidance should not be included in either the sex or the gender identity questions. The NS-DeC response to the paper is published in "NSDEC Minute - Correspondence between November 2020 and January 2021".

Guidance wording

To minimise barriers to completion of the sex question, guidance needs to balance different aims. It needs to:

• direct people in how to answer

• be considerate of people that have identities other than male or female, or have physical sex development that is different to what is generally expected of males and females, who may not wish to answer as either male or female

• accept that respondents may have legal/official documents that state male and legal/official documents that state female

• use terminology that is acceptable to the whole population

Information on "Why we ask this question" has been moved to the top of the page as research found this was important to encourage response (2020:5, 2020:6). This has been applied to guidance for all questions. Within this section, more detail on how the information is used has been added. In addition, within the main body of the text, information on the importance of the question is repeated for further emphasis.

All references to specific population groups have been removed. This ensures that the guidance remains relevant to all potential readers and removes terms that are not universally acceptable to the communities being described.

The direction on how to answer has been amended to align with the target concept being "sex as recorded on legal/official documents" and cognitive testing findings (2020:6). The recommended guidance is:

"If you are considering how to answer, use the sex recorded on one of your legal documents such as a birth certificate, Gender Recognition Certificate, or passport."

The following amendments have been made:

• "considering" replaces "unsure" as participants interpreted "unsure" as meaning we thought they did not know the answer, rather than that they were unsure what concept of sex we were collecting

• "legal documents" replaces "official documents" as participants found this vague, the term "legal" makes it clearer we are referring to government-issued documents

• "birth certificate" has been added as most members of the population would have been issued a birth certificate, whereas previous examples were not as inclusive

• "Gender Recognition Certificate" has been added as not all those who have applied for this have updated their other legal documents

• "driving licence" has been removed as the person's sex is not explicitly recorded on this document

To reduce repetitive content across the online help, information on what to do if you do not want to share a form with your household, and on confidentiality, has been moved to a separate page, accessible through a "Related links" section.

Changes to guidance

This article relates to guidance used in Census 2021 from 22 February to 9 March. From 9 March onwards the guidance line below beginning “If you are considering how to answer” was amended to “If you are considering how to answer, use the sex recorded on your birth certificate or Gender Recognition Certificate.” This change was made in response to a court order and is related to the legislative framework of Census 2021.

Final question guidance

The final guidance for the Census 2021 question “What is your sex?”, will be accessible via the Census website, is as follows:

What is your sex?

Why we ask this question

This question is vital for understanding population growth and equality monitoring. Please select either “Female” or “Male”.

If you are considering how to answer, use the sex recorded on one of your legal documents such as a birth certificate, Gender Recognition Certificate, or passport.

If you are aged 16 years or over, there is a later voluntary question on gender identity. This asks if the gender you identify with is different from your sex registered at birth. If it is different, you can then record your gender identity.

Answering on behalf of someone else

If you are answering for someone else, where possible you should ask them how they would answer. If they are away, select the answer you think they would give.