Where are all the women in economics?

We hear a lot about the under-representation of women in so-called STEM fields - science, technology, engineering and maths.

But the proportion of women in economics is by some measures smaller.

In the US, only about 13% of academic economists in permanent posts are women; in the UK the proportion is only slightly better at 15.5%.

Only one woman has ever won the Nobel Prize in economics - American Elinor Ostrom in 2009.

And there wasn't even a single woman on some of the lists floating about guessing who this year's prize winner would be - it went to the behavioural economist Richard Thaler.

Some have argued that these figures aren't necessarily the result of bias.

Maybe, they say, women are simply behaving rationally and choosing different disciplines that are perhaps more suited to their temperament and skills, or choosing to work in different but related fields.

But Cambridge University economics lecturer Victoria Bateman says that can't really explain all of the gap.

"I think that that way of thinking about the problem is completely false," says Dr Bateman, who is a fellow at Cambridge's Gonville & Caius college.

"But I think [it] helps explain why economists have for too long hushed up this problem.

"Because if economists' models are suggesting that sexism doesn't exist, that it's all a result of people's free choices and... their personal characteristics, then you deny the fact there is a problem."

In fact, there is a growing body of research suggesting that there are some biases - overt and subconscious - that might be contributing to the lack of women in academic economic departments.

A study published by University of California, Berkeley's Alice Wu made waves earlier this year.

Using natural language processing, Wu analyzed over one million posts on a website called EconJobRumors.com, which is a sort of online forum where academic economists discuss job openings and candidates.

Like many places on the internet, the conversations aren't particularly pretty or politically correct.

Wu found that when posters on the site discussed female economists, they used starkly different terms than those that were used to discuss male economists.

Many of those words are incredibly offensive. Posters tended to discuss a woman's physical appearance (hot and hottie were in the top ten) whereas those terms used with men tended to emphasise their intellectual ability (Wharton and Austrian - for the school of economic thinking - were in the top terms for men).

The paper caused a lot of debate within the economic community - with many saying that what people say on the internet isn't necessarily an indication of how they truly think.

University of Bristol professor Sarah Smith says: "I think it's an extreme view. I don't think it's a representation of everyone in the profession."

But, she adds: "I don't think it's surprising when you tie it up with looking at the proportion of women at different levels."

Prof Smith - who is also the chair of the Royal Economic Society's Women's Committee - cites other evidence that suggested a bias against women in the economics profession, such as a paper published by Harvard researcher Heather Sarsons.

That paper found that an additional co-authored paper on an economist's resume correlates to an 8% increase in the probability of a male economist getting a tenured post - but only a 2% increase for female candidates.

Interestingly, the gap decreased if women co-authored papers with other women.

Ms Sarsons wrote in the paper: "While solo-authored papers send a clear signal about one's ability, co-authored papers do not provide specific information about each contributor's skills. I find that women incur a penalty when they co-author that men do not experience."

Her paper, she added in a footnote, was intentionally single-authored.

There are more studies - ones that suggest that female economists' papers take six months longer to peer review in top journals than their male counterparts; that when women get tenured faculty jobs in economics, they get paid less; and that even if a woman makes it to the front of a lecture hall - there might be no men listening to them.

"There was a very interesting and quick bit of number crunching that was done by the Centre for Global Development which has headquarters in both Washington and London," says Cambridge's Dr Bateman.

"When they looked at male attendance at the seminars that they run they found that it fell off quite dramatically whenever gender was mentioned in the seminar topic."

Dr Bateman says the fact that there are so few women at the top has meant that many young women can't view themselves in those positions. She notes that in the early 2000s the proportion of women studying economics in British universities was around 30%.

It's down to just 26% today.

That women aren't even choosing to enter the discipline really surprised me. So I went to Cambridge to speak to some of the current undergraduates in economics.

I met Paulin Nusser, a final year economics, student at the University Centre on a busy Sunday. I asked her what her experience studying economics had been like.

"When I think back to my lectures last year for instance out of the 11 lecturers and supervisors I had throughout the year that are based in the faculty - just one was a woman," she says.

This is why she says it can sometimes be hard to imagine a career in academic economics, even though she hopes to pursue it at postgraduate level.

"Representation is just something that does affect me because I am subconsciously looking for role models or someone where I can say you know, 'oh that could be me standing up there teaching this lecture'."

Clara Starrsjo, a second-year student says she notices that her male and female classmates approach economics problems differently - which often leads to better, more comprehensive answers.

This is why she's become passionate about increasing the number of women who study economics - including meeting with potential female economics students at a Women in Economics day each autumn.

I ask her why she tells these women they should enter the field - even if the odds may seem stacked against them.

"For the moment economists have only looked at the world around them through male eyes and this only provides us with half the story," she says she tells them.

"And with only half the story how can we get results that will help the whole population?"