Norwegian Wood

Three economists (Esther Ann Bøler, Beata Javorcik and Karen-Helene Ulltveit-Moe), study hard and find that your pay will be higher if you meet the needs of your employer better than someone who doesn't.

... the gender wage gap persists partially because firms have an incentive to disproportionately reward individuals who work long and particular hours. Differences in pay between genders may also be due to differences in flexibility and commitment. Moreover, if women are less committed and flexible, globalisation may exacerbate the gender wage gap, because it increases the value of worker flexibility to firms.

Got it; more commitment and flexibility to the employer is key.

By the virtue of being exposed to higher competition, exporters require greater commitment to work and greater flexibility of their employees. For instance, working for an exporting firm may require taking late night phone calls to communicate with customers in different time zones and international travel arranged at a short notice. The employees may be expected to be available around the clock seven days a week in case of unexpected problems arising on the production line or shipments being delayed.

So, expect to be paid more. How unfair;

Thus, working for an exporting firm is associated with closing almost a fifth of the observed gender wage gap. ....

I.e., the gap in the non-export sectors is greater.

This analysis, however, does not take into account unobservable worker characteristics that are likely to be correlated with the choice of working for an exporter. Interestingly, and in line with our hypothesis on gender differences in flexibility and commitment, controlling for unobservable worker characteristics (or unobservable worker-firm heterogeneity) reverses the results.

Unobservable. Except to the people who have to pay for it. Which appears to be a bad thing only if you're  a PhD student at the Centre for Equality, Social Organization and Performance (ESOP) in the Department of Economics, University of Oslo.