Many investigations have taken place into why there is a gender gap at work, in terms of pay and in terms of why men are overrepresented in senior positions in the workplace.

One of the main problems with studying the gap is gaining access to workplaces. Research has tended to rely on self-reported data such as surveys.

A new study, however, was given unprecedented access to one workplace where women were underrepresented in upper management. Women in the company made up around 35-40 percent of the entry-level staff, but by top senior levels, they had just 20 percent of the roles. 

Researchers were allowed to collect a huge amount of data by looking at email communication and meeting schedules, and by attaching sensors to the workers to measure their behavior extremely precisely. The team, from data analytics company Humanyze, used the sensors to measure everything from the amount of time workers spent interacting with their co-workers to the volume and tone of their voices during these interactions.

The results of the survey offer an all too familiar, and frankly quite depressing explanation. 

The sensors, attached to badges, were given to 100 employees within the unnamed company. They were made to look like normal ID badges, to ensure that their presence wouldn't cause people to act differently around those wearing them.

This gave the researchers, who wrote about their research in Harvard Business Review, a huge amount of data to look at. They could test out, for example, the hypothesis that women weren't progressing because they weren't allowed enough face to face access to managers, or that they spent less time with mentors.

When they looked into the stats, however, they found something odd.

"As we analyzed our data, we found almost no perceptible differences in the behavior of men and women," the researchers wrote in Harvard Business Review.

"Women had the same number of contacts as men, they spent as much time with senior leadership, and they allocated their time similarly to men in the same role."

As they looked at the data, they found that men and women didn't vary in the amount of time they spent online and had statistically identical scores in performance evaluations. All in all, their work patterns were "indistinguishable".

So the mystery remained why men were getting promotions and women weren't. The researchers in this fascinating study had an all too depressing explanation for the difference.

"Gender inequality is due to bias, not differences in behavior," they wrote.

"Bias, as we define it, occurs when two groups of people act identically but are treated differently. Our data implies that gender differences may lie not in how women act but in how people perceive their actions."

Essentially, men and women within the company were acting in exactly the same way, but being rewarded differently. Women did the same work as men and performed as well as them, but men got the reward from their (largely male) bosses.

The researchers suggested that companies wanting to reduce gender differences need to look at where the problem is occurring within their own organization (e.g. do women tend to move jobs at a certain point in their career?) and develop bias-reduction programs to specifically tackle the problem.