For both jobs, more females replied to both job listings than males. Of the applicants to the sports assistant position, 53.5% of those interested were women. The generic job listing was split 80-20 females to male. Here’s the interesting part: for both jobs, when the element of the bonus was added, males were far more likely to actually send in their application than females. Or worded the other way around, females were more likely to pass on the job once they found out part of their pay would be based on their performance versus a co-worker. In the most competitive salary structure, where the base pay was $12 an hour and the bonus $6, List determined that men were 55.5% more likely to apply for the job than women. The conclusion: Women don’t like competition.

How does this relate to the gender gap? List says, anecdotally at least, it appears the industries and positions with the most competitive work environments tend to pay the most. Lise Vesterlund, an economist at the University of Pittsburgh, says she has observed the competition gap in her research as well. And she says it can have broad implications for the salaries and the careers of women in any industry. Many promotions, for instance, are the result of employees going to their bosses and telling them they are outperforming other workers. CEO succession often involves two or three top employees in an open competition for the head job. If women don’t like to compete, they are less likely to put themselves in these types of situation. That can allow less capable male workers to end up with the better job titles and bigger pay checks.