A rigorous new study by Ghazala Azmat and Rosa Ferrer finds that much of the difference in employment outcomes between male and female law firm associates is attributable to men billing more hours (not simply working more hours; doing more work that is billable), bringing in more revenue, and having greater aspirations to make partner. (Summary available here).

After controlling for these differences, there is still evidence consistent with some sex discrimination (albeit directional and no longer statistically significant), but discrimination appears to be far less severe than many earlier studies had suggested.  Those earlier studies had less information about differences in employee performance. Questions remain about whether discrimination could lead female law firm associates to have fewer opportunities to do billable work or to network and generate business, although Azmat and Ferrer find some evidence against this.  Consistent with previous studies, child-rearing has a more negative impact on women than on men through greater reductions in work hours and revenue generation.

The results suggest that ambitious associates–of either sex–can increase their chances of making partner by prioritizing billable work and revenue generation over other uses of their time.