High profile sexual discrimination cases have been brought against Facebook, Twitter and tech VC firm Kleiner Perkins this month. The cases are damaging to an industry trying to make itself more female-friendly, but a new report suggests that these might not be isolated cases but rather part of a trend.

The new report from the American Association of University Women (AAUW) shows that the gender gap in Silicon Valley is actually widening. It claims that women in the industry are being held back by stereotypes and biases.

"What we found is that not only are the numbers low, they are headed in the wrong direction," says Catherine Hill, AAUW's vice president for research. In 1990, 36 per cent of employees in computing were women and that number fell to just 26 percent in 2013. The study found that just 12 percent of engineers are women, a slight increase from 9 percent in 1990 but that figure is for all engineers rather than computer engineers.

Over the same period the number of women working in biological and chemical science positions have increased but computing is the outlier. The statistics for women from ethnic minorities make for even bleaker reading. In 2013, just one percent of engineers and three percent of computing professionals were black women, while hispanic women made up just one percent of both work forces.

As part of the study, science faculty members were asked to evaluate resumes that were identical apart from the names. The research found that both female and male faculty members were more likely to choose the resume with the male name and also offered male candidates higher salaries for the hypothetical jobs.

These stereotypes also discourage young women from studying these fields. Despite the boom in the IT industry over the last few years the number of female computer science graduates has actually dropped from 19 percent in 2007 to 18 percent today.

The co-authors of the report discuss the findings in detail in the video below.

Photo: Michael Coghlan | Flickr