The old boys’ clubs of business are becoming a relic of the past, but some gender inequalities persist in subtle ways. It goes without saying that teamwork and being able to work well with colleagues of any gender is a prerequisite for jobs today. What’s not so clear, though, is how women fare when it comes to getting credit for group work.

A new study conducted by Harvard researchers gathered data on economists to see how teaming up with others to co-author papers affects the likelihood of getting promoted (in this case, tenure). Turns out, working with others – especially men – on a project is correlated to lower rates of promotion for women compared to men. Women essentially experience a collaboration penalty, says lead researcher Heather Sarsons.

Women who solo author all their papers have roughly the same chance of receiving tenure as a man, according to the study. This gap widens as more co-authors are added, eventually reaching a point where women had a 40 per cent probability of receiving tenure compared to 75 per cent for men. Sarsons and her team found that on average women are 18 per cent less likely to receive tenure than men.

It’s tough to untangle whether the co-authoring penalty comes from employers not giving women as much credit for their work when they collaborate with men or if women are less likely to take credit for their work. There is evidence to support both scenarios, but what is clear is that when there is ambiguity around who did what work during a group project, men are favoured unfairly.

Results like these are interesting, especially when pulled up against studies that have demonstrated the benefits of men and women working on teams together. One study conducted by the London Business School of 100 teams of knowledge workers from 17 countries found that teams split equally between men and women were more likely to share knowledge, experiment and fulfil tasks. This is a result of what researchers coined the “safe communication climate” created by balanced work teams, which in turn drives innovation.

Another Harvard study, this one from 2013, found that teams with equal numbers of men and women performed better than male-dominated teams, while female-dominated teams had no corresponding decrease in productivity or performance.

“We thought this bias might hurt people when it’s not really clear who did what on a project,” Sarsons says. “My hope with this is not that women work in groups less. It is to bring attention to the fact that people might unconsciously be assigning credit for things differentially.”

The results of this study and similar ones are particularly relevant, as more jobs require teamwork and collaboration on projects. Work doesn’t always speak for itself, so employers and employees must be vigilant about assigning and claiming credit where credit is due.