There was an advertisement circulating on Twitter last week in which clothes retailer The Gap made a pitch for the academic customer-base.

Accompanying a picture of a woman in skinny chinos (very Gap), high heels and an unstructured blue jacket, the text of the advert read: ¡°The tenure-track professor. Get respect for your ideas and blazer choices.¡± The woman in question wasn¡¯t wearing glasses, but a pair had been overlaid to give her added professorial gravitas.

In one droll response, an academic posted: ¡°I was so worried about what I would wear today! Thanks @Gap for the inspiration! My ideas will be heard in that blazer!¡±

This may not be the most egregious example, but it¡¯s a little reminder that female scholars face countless everyday challenges, barriers and frustrations that their male counterparts do not ¨C and often can¡¯t imagine.

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But no one can argue that pay is one of those hidden inequalities ¨C it is plain for all to see.

In our cover story, we take a detailed look at pay across the UK higher education sector, focusing in particular on the disparities that persist between men and women, as well as the issues facing minority ethnic staff.

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The findings will come as no huge surprise, not least because this has been a problem for years and it is not one that will be resolved overnight.

For all academics, the pay gap has fallen steadily over the past five years, but it still stood at 10.5 per cent in 2015-16. It¡¯s worth saying that since the proportion of female staff declines with seniority, this is not direct evidence of disparities affecting people who are in equivalent jobs.

However, our analysis also examines how professorial pay stacks up, allowing a meaningful comparison of men and women in like-for-like roles.

There¡¯s an argument that professorial pay is likely to be more prone to inequality than more junior grades because it is not governed by the national pay spine. If male applicants or incumbents are more aggressive and successful in negotiating for higher pay, for example, then it¡¯s at the professorial level that this is likely to come through in the data.

It¡¯s also worth noting that when the University of Essex decided last year to do something big to tackle the gender pay gap, its analysis suggested that it was at the professorial level that action was most urgent (Essex issued a one-off pay rise to bring its female professors into line with their male colleagues).

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What our study finds is that the pay gap among professors is indeed persisting. Surprisingly given the profile that the issue now has, it actually got a little worse this year.

It¡¯s possible that this is not the damning indictment that it sounds. Universities may be taking action to improve the gender balance of the professoriate by promoting more women, for example, who as new professors would tend to be at the lower end of the salary scale.

However, there¡¯s no way of knowing whether this is the case. And this very often is the problem with tackling issues of inequality ¨C the not knowing.

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When Liz Schafer took a stand against the issue at Royal Holloway, University of London a decade ago, she was forced to go through a gruelling tribunal process to extract information about how the pay of male and female colleagues varied.

The result was a new professorial pay banding system and a ?10,000 pay rise for Schafer, which as she wrote at the time demonstrated that her previous salary was not appropriate.

Transparency on pay at the individual level is, with the exception of very senior managers, something that is unlikely to become the norm any time soon.

But there is a need for greater clarity on how the biases and barriers that clearly exist manifest themselves in pay, as well as the broader issue of promotion and representation of women within the upper echelons of academia.

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It shouldn¡¯t take an unstructured jacket or a trendy pair of specs for universities to understand how important this is ¨C it should be blindingly obvious.

john.gill@timeshighereducation.com