What was the spur for writing the book?

It was almost inevitable that I ended up writing this book, given that the gender data gap is a real thing. And because of the way that I came into feminism, which was discovering that I had a gender data gap in my own head.

I went from having not been a feminist at all – having been quite a misogynist, and fully buying into the cultural representation of women, but thinking that I was different: not trivial or silly or over emotional, like other women. I was more like a man. Then I went to university and read a book on feminism and linguistic theory. I read about the generic male in language and how in using ‘he’ to mean he or she, ‘man’ means humankind. Because no one had ever said that to me before, I hadn’t noticed. I realized: ‘Oh, my God, when I imagine professionals, I am picturing men’. I realized that it wasn’t just these words, it was also with supposedly gender-neutral words such as ‘doctor’ and ‘professor’, ‘journalist’ and ‘politician’. I was really shocked. Once I started thinking that perhaps this could explain why, despite not actually knowing any women that really fit the classic stereotype of women portrayed on film or in magazines, I still subscribed to that view of women. I remember feeling incredibly angry that I had been made to feel ashamed of my sex. And that I needed to prove I was different, that I was not like my sex, in order to be taken seriously and treated like a human being.

And why do you think highlighting the gender data gap is particularly relevant now?

Well the things that have really got me going, are always about the under-representation or misrepresentation of women. People ask me: what’s your next campaign going to be? What are you going to do next? And I don’t know, because every time I’ve started something, it’s because something has made me angry. And the common thread is the lack of representation of women – on banknotes or in statues – and now, coming across the fact that women aren’t even represented in data.

That was why I responded in the way I did when I first discovered the facts around female heart attack symptoms. When I was researching my first book, I discovered that female heart attack symptoms, which I had always been taught were gender neutral heart attack symptoms, such as pain in the chest and down the left arm, are not what a lot of women experience when they are having a heart attack. In fact, only one in eight women will experience chest pain. Instead, women suffer what feels like indigestion, nausea, fatigue and restlessness. So a lot of women do not realize they are having a heart attack. And doctors are misdiagnosing women. And that is partly because very typical female symptoms are still labelled as atypical even though they are not at all atypical for women. The result of all of this is that women are more likely to die from a heart attack than men, and have been since 1984. It is one of the leading causes of death in women. In the US, heart attacks have been the leading cause of death among women since 1989.

I also discovered that the US Food and Drug Administration had, in 2013, advised women to half their dose of Ambien, a popular sleeping pill, because women were metabolizing the active ingredients twice as slowly as men. This meant that the dosage was double what it should be for women and, as a result, they were driving to work the next day still under the influence of the drug and crashing their cars. By this point, as you can probably imagine, I was absolutely furious. I just didn’t understand how this was happening. Why the hell weren’t we were talking about this? It just seems so incredibly shocking to me. So I started looking into it.

Was there any one case that shocked you in particular?

Not a particular example because they are all incredibly shocking. It is very difficult to pick one. What I did find unnerving were the excuses used as to why women were not factored in to drug trials. Someone had decided at this point that women were too complicated. Our travel patterns were too complicated. The way we manage our paid and unpaid work was too complicated. Our bodies were too complicated. This is the number one reason why medical research is not done on female animals or humans: we are too complicated.

How do you get people to address these gaps? Because solutions cost money.

Yes they do cost money, but they also save money in other areas. Women make up the majority of bus users in London, with the exception of the night bus, because women don’t feel safe on it. So if Transport for London could come up with a solution that made women feel safer more would use the night bus and the transport authority would make more money.

The first thing that needs to be done is to collect the data. I actually can’t answer the question properly because we don’t have the data. And if we did, we would know why women aren’t using night buses. What we need to do is to collect sex disaggregated data so that we can allocate resources in a way that makes sense, because we currently are not doing that.

And we need to look at how we design and measure the economy, how we design the world. Our gross domestic product statistic is hopelessly inaccurate because it doesn’t account for all the unpaid work women do. GDP is one of the most important figures for every country. We make economic decisions based on this figure even though it does not reflect reality.

What has the reaction been to the book?

It has been really positive. I think the overwhelming reaction from women has been relief. Suddenly things make sense and women realisze that there is nothing wrong with them. It is simply that the world has not been designed for them.

I am really pleased that so many women are having this realization but I am also angry. How many of us adjusted to accepting that there was just something wrong with us, when actually it was just that we were supposed to fit into a world that had not been designed to fit our body.

Men sometimes say: ‘Oh, well, I’m 6ft 7in and 20 stone. Things don’t fit me either’. Which is totally missing the point. They are an excetion, they are an outlier. Women are not outliers. In a way, it kind of makes the arguement for me, because it shows how heavily ingrained this idea that women are atypical is, when we’re not atypical. We are 50 per cent of the population.

Your last two campaigns − to get a woman on a banknote and a statue of a woman put up in Parliament Square − were trying to achieve specific things. This book feels much broader. Has there been a shift in your campaigning or do you think that they are all related?

They are completely related. It is 100 per cent a continuation. It is all about seeing the male as the default. It is all about challenging that. The campaigns needed to be specific and small, but they are about a much bigger issue. This is a book, so, I can set out the whole argument for why the gender data gap exists.

It is the same argument behind why we have an all male line-up on banknotes and an all male line-up of statues in Parliament Square. We just don’t realize that we are representing humanity as male because we are so used to the idea. Every campaign of mine has been about challenging this premise.

I’m always trying to open people’s eyes to the fact that this is going on, that we treat women as if they don’t exist or are at best a less important minority. That has some serious consequences and this is what the book is about. It isn’t just about women feeling they can’t achieve things. This gap is affecting women’s health. And women are dying.

How did you go about collecting the data for this book? And were there parts that were easier to search than others?

It was all quite difficult to be honest bcause it was about trying to find out what we didn’t know. It is quite difficult to discover what we don’t know. So I made use of experts and they were very helpful. It was a mixture of following my nose and a lot of reading of newspapers to see what was being reported, and then reading the original studies and asking experts to guide me. It was three years of work.

How did you decide where to start?

The difficulty was where to start and how to organize it. Everything is so interlinked. I can’t emphasize enough how difficult this book was to wrestle into a manageable, coherent thesis rather than just: ‘Here’s a thing, and here’s another thing.’

What would you like to see happen as a result of your book?

Since it has been published, people have been in touch to say that they are taking these new insights into the workplace, and that they are changing the way they are approaching projects. Or that they made this specific change in a project that they were working on because they now realized that it was biased towards men.

And I can’t tell you how amazing that feels. But the job is huge. It requires everyone in any sort of position of power, anyone who is involved in product design of any kind, any researcher in any field, to be aware that this is an issue that they need to factor in.