Where sex matters | Data and statistics

Data and statistics

We need accurate data, disaggregated by sex in order to understand differences in the lives of women and men.

Sex is a powerful predictor of almost every dimension of social life including education, employment, crime, physical and mental health. It is difficult to think of an area of life where sex is not an important dimension for analysis.

As Caroline Criado Perez has pointed out, if data is not collected on men and on women then systems – from transportation to medicines and medical devices to tax structures and consumer products – tend to ignore the needs of women, and ”when your big data is corrupted by big silences, the truths you get are half-truths, at best.”

What is the problem

Increasingly, accurate data collection on sex is being undermined by the conflation of sex, gender and gender identity.

The principle of self-ID has been accepted by many public bodies, replacing sex with self-identified gender when recording crimes and organisational pay-gaps, on medical records and in the census.

All three of the UK census authorities (for England and Wales, Scotland and Northern Ireland) intend to carry guidance to accompany the sex question in the next census which instructs respondents to answer based on their self-declared gender identity, not on their natal sex or their GRC administrative sex.

Jonathan Portes, former chief economist at the Department for Work and Pensions, has said this move would make it much more difficult to track and tackle issues such as the gender pay gap and inequality in childcare, social care, housing and health.


  • Getting it right: diversity and inclusion

    The business risk of misaligned D&I

    Sex matters in the City

    16th December 2021

  • X passports appeal dismissed

    The Supreme Court has unanimously dismissed Christie Elan-Cane’s case for an “X” passport. The judgment states  “There is no judgment of the European Court of Human Rights which establishes a positive obligation to recognise a gender category other than male or female, and none which would require the Secretary...

    15th December 2021

  • No need for sex data on domestic abuse?

    Yesterday the Domestic Abuse Commissioner launched a survey for survivors of domestic abuse about their experience of using domestic abuse services across England and Wales: “We are running this survey so that we can understand what is good about domestic abuse services in different areas of the country, and...

    7th December 2021

  • Sex matters in the City

    The Financial Conduct Authority is the regulator for the financial services sector in the UK. They are proposing to set new rules to encourage big companies to have more “female” directors on their boards. The new regulations would cover over 1000 firms, employing tens of millions of people, and...

    19th October 2021

  • Fighting for the principle of collecting data on biological sex

    A guest post by MurrayBlackburnMackenzie. Scottish Parliament Public Petition: Call for signatures In early June MurrayBlackburnMackenzie (MBM) lodged a petition with the Scottish Parliament Public Petitions Committee. It calls on the Scottish government to require Police Scotland to accurately record the sex of people charged or convicted of rape...

    27th June 2021

  • Truth and reconciliation

    How should the public sector leave the Stonewall Champions Scheme?

    6th June 2021

  • Time to #LeaveStonewall

    This is the letter we have sent to the CEOs of the 850 organisations that are members of the Stonewall Diversity Champions Scheme. Re: Leaving the Stonewall Diversity Champions Scheme We are writing to call on you to withdraw from the scheme, both for the sake of your own...

    29th May 2021

  • Sex, gender and medical data: a way forward

    Susan Bewley, Margaret McCartney, Catherine Meads and Amy Rogers published an article in the British Medical Journal calling for clarity about sex and gender in medical records and data.

    This a "rapid response" from Sex Matters co-founder Maya Forstater that was published online by the BMJ.

    23rd March 2021

  • NHS: let’s talk about sex

    This tweet by Emma Parnell, Lead Service Designer at NHS Digital and the associated Medium post “Lets Talk About Sex” is interesting. Parnell writes in detail about how she worked to remove the question of whether a patient is male or female from the online system for booking COVID...

    20th March 2021

  • Sex (or gender?) as a hate crime: why the rush?

    The push to adopt a gender neutral definition of “misogyny” as a hate crime with amendment 87B to the Domestic Abuse Bill (being debated this afternoon in the House of Lords) is another attempt at the political erasure of sex. Why the rush when the Law Commission is working...

    17th March 2021

  • Census guidance on the sex question ruled unlawful

    Census day is 21 March 2021. Yesterday, in a challenge brought by Fair Play For Women, the High Court ordered the Office for National Statistics to correct the guidance they provide online about how to answer the question “What is your sex?”   Until yesterday, the guidance for the 2021...

    10th March 2021

  • ONS reverses decision to ask clear sex question on the census

    The ONS has reversed its decision not to allow self-identified answers to the sex question in next month’s Census. On 22 January, 2021 The UK’s Chief Statistician, Professor Ian Diamond, confirmed on BBC Radio 4’s Today program the question “what is your sex” should be answered according to someone’s LEGAL SEX,...

    12th February 2021


  • Frontiers in Global Women's Health

    Effective communication about pregnancy, birth, lactation, breastfeeding and newborn care: the importance of sexed language

    Karleen D. Gribble, Melissa C. Bartick, Roger Mathisen, Shawn Walker, Jennifer Gamble, Nils J. Bergmann, Arun Gupta, Susan Bewley, Jennifer J. Hocking and Hannah G. Dahlen in Frontiers


  • The Supreme Court

    Passports must show M or F for sex

    An appeal was made to the Supreme Court after the Court of Appeal had concluded that an applicant for a passport must declare their gender/sex as being either male or female, not “unspecified” (“X”).


  • Stats for gender .org

    Stats for gender

    Genspect, an organisation which supports parents with gender-questioning kids, created this website because it believes that the public has a right to reliable data, intuitively categorised, and phrased in simple, jargon-free terms, and wants those who are questioning their gender to have full access to the facts.


  • Legal Feminist responds to FCA consultations

    Legal Feminist applauds the intention behind the proposals, and is a strong proponent of data-driven policy-making, but felt that the way in which those intentions were to be reflected in rules and policy rendered the proposals at best ineffective and at worst dangerous.


  • The Political Quarterly

    Sex and the Office for National Statistics: a case study in policy capture

    How did the ONS end up in court defending its guidance on a question which most people would deem self-explanatory? Alice Sullivan explains the legislative and political context around gender recognition, and the consequences for data collection. 


  • HM Passport Office


  • Swedish cohort study on sex reassignment

    Long-Term Follow-Up of Transsexual Persons Undergoing Sex Reassignment Surgery: Cohort Study in SwedenDhejne C, Lichtenstein P, Boman M, Johansson ALV, Långström N, et al. (2011) Long-Term Follow-Up of Transsexual Persons Undergoing Sex Reassignment Surgery: Cohort Study in Sweden. PLOS ONE 6(2): e16885. 


  • WPUK – Woman's Place UK

    Women count, count women: webinar

    Keeping the category of sex mandatory and clear in the census was a campaigning priority of Woman’s Place UK from 2017. In October 2020 they hosted a webinar on the census with Alice Sullivan, Lisa Mackenzie, Jane Clare Jones and Selina Todd.


  • The Times

    Open letter on the census

    On December 15 2019, 80 of the UK’s leading social scientists wrote an open letter, which was published in the Times, listing their concerns about letting census respondents list their self-identified gender.


  • The Political Erasure of Sex

    The Political Erasure of Sex

    Jane Clare Jones with Lucy MacKenzie (2020), Oxford University The first in a series, this report ‘Sex and the Census’ focuses on planned changes to the way that data on sex is collected in the UK census and outlines why collecting census data on males and females matters.


  • Murray Blackburn Mackenzie

    Murray Blackburn Mackenzie

    MurrayBlackburnMackenzie is an independent policy analysis collective. Its work on proposals for the 2021 UK census and related research has been cited in the Scottish Parliament and informed parliamentary questions and debate.