Separating sex and gender is statistical malpractice – Notes from a data witch

On August 11 2026, it will be Census night in Australia. The Census is an important instrument for collecting data on the Australian population, and informs policy decisions at every level. It is conducted by the Australian Bureau of Statistics, and they are an extremely professional organisation that takes their work seriously. Every time a new Census is conducted, they reconsider the questions it asks and will make changes from time to time in order to suit a policy environment that changes over time. They are diligent, and they research their questions very carefully.

For the 2026 Census there are two new optional questions that have been introduced, applicable only to people over the age of 16. Both of these questions relate to Australia’s LGBTQIA+ population. One of the new questions allows people to specify their sexual orientation. This post is not about that question.1 Rather, I want to talk about the second question, which allows people to specify their gender identity if they would like to.

The intention behind the two questions is clear: the sexual orientation question has been added to allow policy decisions about the LGB population to be informed by the census, whereas the gender identity question exists to inform policies related to the T subgroup of the LGBTQIA+ population. These questions were added on the advice of academics, LGBTIQA+ advocacy organisations, and they have been extensively praised in the progressive, left-leaning, and queer media (e.g., here, here, here, and here). Taken at face value, you would be tempted to conclude that the new gender identity question is a step forward for transgender inclusion in Australia.

It is not. In this post, I hope to convince you of the exact opposite claim: somewhat counterintuitively, the new question is catastrophically bad for transgender people. It is dangerous, it puts our safety at risk, and borders on statistical malpractice. It should not have been added, and in future it should be removed.2

An anecdote

I’ll start the post with an anecdote to illustrate why I am making this claim. A few weeks ago I had to find a new GP. I’d been with the same practice for many years and was happy with them, but I’ve moved apartments and needed to find something closer to home. After a little research I discovered one extremely close to where I live, so I decided to make an appointment to get a prescription renewed. As with all medical practices, this one has a patient intake form. Because it is the 21st century, the form was online. Being a diligent person I started to fill it out. Within minutes I ran into a problem: just like the forthcoming ABS Census, the clinic separates sex and gender on their forms. In fact, the wording on the questions was almost word-for-word identical to what the ABS now puts on the Census:

Question 1 (mandatory): What is your sex, as originally recorded on your birth certificate? Response options are limited to “male” and “female”.

Question 2 (optional): How do you describe your gender? Several options were presented, including many that are appropriate for trans people.

There was also an optional question about pronouns, but it’s not relevant to the story.

As a middle-aged trans woman who transitioned over a decade ago, and who has a lot of professional experience with the collection of confidential medical data, psychological measurement, and a lot of direct personal experience with how organisations handle data that pertain to transgender people, I stared at these questions with a sense of utter dread. Everything in my professional and personal experience screamed at me that the correct thing to do here was to lie on the birth sex question and select “female”. But my conscientiousness overruled my better judgement and I did as I was asked. I selected “male”.

Within 24 hours, the medical practice had nonconsensually disclosed my transgender status to third parties who have absolutely no right to this information. This is of course a blatant violation of medical ethics, but those ethical standards don’t seem to apply to transgender people: our privacy does not get taken seriously, and I confess that I am rather bitter about it.

How did this happen? You might be tempted to think that it must have been malicious. Perhaps I had a bad doctor, one who does not take her professional responsibilities seriously. This is not what happened at all. What happened is something much, much worse: the underlying database that stores the intake data is configured incorrectly,3 and systems that interact with that database will leak transgender status by design. It is not a “one bad apple” problem: the entire infrastructure that underpins the “sex/gender” data collection is broken, and dangerously so.

Here’s the mechanics of how it happens. Internally, the database stores sex and gender as separate fields, mirroring the intake form: there is a sex...