it's not just a matter of humanities vs. science, or education vs. business, either. In an e-mail, Arreola told me, "The same gap is often seen within engineering itself. Bioengineering has been growing to the point where we could see a 50/50 split of women and men majoring, and there have been some reports of salary staying flat or going down. Engineering fields where women are less than 20 percent pay more."