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.” – (where is this quote from?)

Does sex mean one thing if you are trans and another thing if you aren’t? What does changing your sex mean for crime data? For medical data? For employment data? Does changing your sex mean you actually change your sex or not?
Caroline Criado Perez, Author, Invisible Women
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 of sex with self identified gender in recording crimes, 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 wither 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.

“It’s difficult to think of a public policy area where that data is not relevant”
Jonathan Portes, Former Chief Economist, Department of Work and Pensions
Updates
Resources
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Gender Markers in Passports: Internal review of existing arrangements and possible future options
Report by HM Passport Office, 2014
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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....
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Woman’s Place UK
Woman’s Place UK was set up September 2017 to ensure women’s voices would be heard in the consultation on...
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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: “As social...
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The Political Erasure of Sex
Jane Claire Jones and Lucy MacKenzie (2020) Oxford University This report focuses on planned changes to the way that...
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Murray Blackburn Mackenzie
MurrayBlackburnMackenzie is an independent policy analysis collective. Their work on proposals for the 2021 UK census and related research...