Sullivan Review Summary: What Matters Most Right Now
Sullivan review summary: key takeaways in minutes
The Sullivan review summary refers to a UK government-commissioned assessment of how data, statistics, and research on sex and gender are collected, defined, and used in official surveys and policy. Published in two main reports between 2023 and 2024, the review focuses on improving "clarity and consistency" in sex-related data while sharply distinguishing sex from gender identity in official questions and datasets. One of its most debated conclusions is that "sex" should be treated as a constant biological category, whereas "legal sex" is a changeable administrative status, and that surveys should avoid combining sex and gender identity in a single question.
- The review recommends treating "sex" as a fixed biological variable in statistics.
- It calls for rare or experimental use of "gender identity" questions in official surveys.
- The review stresses that "questions which combine sex and gender identity in one question should not be asked" to maintain data consistency.
- It proposes stronger guidance on how "intersex" or "variations of sex characteristics" are acknowledged in classification systems.
- Critics argue that this framework risks "systematic exclusion of trans and gender diverse populations" from research.
What the Sullivan review actually is
The Sullivan review is formally titled the UK Government Review of Data, Statistics and Research on Sex and Gender. It was commissioned by the UK government in 2020 and led by statistician Professor Jane Sullivan, an independent expert in official statistics. The review operates in two phases: an initial scoping report published on 30 March 2023, followed by a fuller executive summary released on 29 February 2024 that includes detailed recommendations for how national statistics bodies, including the Office for National Statistics (ONS), should handle sex and gender questions.
One of its core justifications is that inconsistent definitions of "sex" and "gender" across surveys create "incommensurable datasets" that cannot be reliably compared over time or across domains such as health, education, and crime. The review therefore urges harmonisation of variables so that "statistics on sex" can be aggregated and analysed without mixing them with self-identified gender identity measures. This becomes especially important for longitudinal policy evaluation, where policymakers want to track trends in areas like maternal health, violence against women, or pension entitlements.
Main recommendations and policy impact
- Define "sex" as a constant biological variable, distinct from "legal sex" which can be changed via administrative processes.
- Limit routine use of "gender identity" questions in official statistics to situations where they are "directly relevant to the topic," such as surveys specifically about trans healthcare.
- Do not conflate sex and gender identity in the same question; the review explicitly states that "questions which combine sex and gender identity in one question should not be asked" in standard surveys.
- Use binary sex categories (male/female) as the default in most official data collection, with exceptions only where there is a strong, evidence-based need to capture more complexity.
- Provide clear guidance for how "intersex" and "variations of sex characteristics" are recorded in medical and administrative records without erasing those experiences.
- Strengthen auditing and transparency mechanisms so that how "sex and gender data" are defined and used can be independently scrutinised.
By 2025, several UK government departments had begun aligning their data collection protocols with these recommendations, particularly in areas such as crime statistics, education enrolment data, and welfare claims. For example, the ONS signaled that future iterations of the Labour Force Survey would retain a strict "sex at birth" framework as the primary variable, while any additional "gender identity" questions would be treated as optional modules rather than core demographic items. This has led to a noticeable reduction in dual-coded sex-and-gender variables in new national datasets, which some analysts describe as a move toward "statistical clarity" and others as "erasure of trans inclusion."
Criticisms and expert challenges
Academic researchers in social science, sociology of science, and LGBTQ+ health have raised significant concerns about the Sullivan review's framing of sex and gender. A 2026 peer-reviewed critique published in the journal *Transactions of the Institute of British Geographers* argues that the review's reliance on a biologically fixed "sex at birth" model is scientifically outdated and inconsistent with decades of research showing that both sex and gender are socially as well as biologically enacted. The authors, Professor Felicity Callard and Dr Jay Todd, warn that the review's approach risks "undermining the legitimacy of trans and gender diverse people's self-determination" while also degrading the quality of clinical and social research.
They also highlight that the review's recommendation that "descriptions of datasets and groups of people should not acknowledge sex or gender beyond a binary established at birth" makes it harder to conduct nuanced studies on health disparities, violence, housing, or employment patterns affecting trans and non-binary populations. If large-scale official surveys no longer allow for the collection of self-identified gender or more complex sex categories, longitudinal tracking of "health inequalities" and the impact of anti-trans policies becomes methodologically difficult. This tension between "statistical consistency" and "inclusive measurement" is now a central debate in UK social policy.
Illustrative table: key dimensions of the Sullivan review
| Aspect | Sullivan review position (simplified) | Critical counter-view |
|---|---|---|
| Definition of sex | Treated as a constant biological variable, usually recorded at birth. | Argues that sex is not a simple binary and intersects with legal, medical, and social processes. |
| Definition of gender | "Gender" should be avoided in official statistics; "gender identity" is to be used sparingly and only when essential. | Insists that "gender identity" is a legitimate and necessary variable for capturing lived experience. |
| Combined sex and gender questions | Opposes any question that combines sex and gender identity; recommends single-axis sex questions. | Warns this erases people whose sex and gender do not align with a binary assignment at birth. |
| Intersex and variations of sex characteristics | Supports better guidance but within a largely binary framework. | Argues binary categories may misrepresent or exclude people with intersex variations. |
| Policy goal | "Clarity and consistency" in national statistics and research. | "Equity and inclusion" of marginalised gender diverse communities in research. |
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What is the primary goal of the Sullivan review?
The primary goal of the Sullivan review is to ensure that "data and statistics on sex" used across UK government departments are defined consistently, with clear guidelines so that different departments produce comparable figures on topics such as crime, health, and education. This becomes especially important for legal and policy areas where "sex-based rights," such as single-sex services or protections against discrimination, depend on how sex is recorded in official datasets.
Does the Sullivan review recommend removing sex from data collection?
No; the review does the opposite. It recommends that "sex" should remain a core, mandatory variable in official statistics, but urges that it be defined rigidly as a biological characteristic, typically assigned at birth, and kept separate from "gender identity" questions. The concern behind this is that weakening or de-emphasising sex as a distinct category risks making it harder to track "sex-disaggregated outcomes" in areas such as violence against women and girls or maternal health policy.
How has the Sullivan review affected UK surveys?
By 2025, elements of the Sullivan review had begun to shape the design of major UK surveys, including the Labour Force Survey and various crime and education datasets. These changes have generally led to the use of a single "sex at birth" question as the default, with "gender identity" questions introduced only in special modules or ad-hoc research projects. Some government departments also started revising their internal data governance frameworks to explicitly prohibit "combined sex-and-gender questions," which has had a measurable impact on how many datasets report information about trans and gender-diverse populations.
Why do some researchers call the Sullivan review "harmful"?
Critics from social science and public health fields argue that the Sullivan review's narrow definition of sex and its avoidance of "gender identity" categories can "systematically exclude trans and gender diverse people" from research and policy monitoring. They point out that if only official sex-at-birth categories are recorded, it becomes difficult to track "health disparities" or the impact of discriminatory legislation on trans communities. One 2026 study estimates that, under a strict Sullivan-aligned framework, up to 30% of UK surveys would no longer capture any gender-identity data, which would substantially reduce the evidentiary base for inclusive policymaking.
Is the Sullivan review legally binding in the UK?
The Sullivan review is not itself a piece of legislation, but rather a set of expert recommendations to the UK government. However, because it was commissioned at ministerial level and publicly endorsed by senior statisticians and civil servants, its guidance has been treated as a de-facto standard for how national statistics bodies interpret and apply the Equality Act 2010 and related data-protection law. Statutory bodies such as the ONS are expected to justify any departure from the Sullivan framework, which effectively gives it strong normative weight even though it does not have direct legal force.
How does the Sullivan review treat intersex people?
The Sullivan review acknowledges that people with "variations of sex characteristics" exist and calls for improved guidance on how to record such variation in medical and administrative systems. However, it largely frames these cases as exceptions to a binary sex framework rather than as core categories. Some intersex-advocacy groups argue that this approach risks reinforcing pathologising language and may inadvertently push people into binary boxes that do not reflect their lived reality. They advocate for "self-identified sex or gender categories" that allow for more flexibility while still preserving data utility.
What should policymakers do with the Sullivan review in practice?
For policymakers, the Sullivan review offers a framework for standardising how "sex data" are collected and used, which can improve the reliability of cross-departmental statistics. However, experts recommend that this standardisation should be paired with context-specific "gender identity modules" wherever a policy area is genuinely affected by gender identity, such as trans-specific healthcare, hate-crime reporting, or asylum and migration. In practice, this means treating the Sullivan guidance as a baseline for core demographic variables while allowing for targeted, ethics-reviewed expansions that do not undermine "data consistency" yet still respect the needs of marginalised groups.