gender gap in service

I'm sure you'll all be shocked to hear that a new study shows a significant gender gap in the hours of service per week among tenure-track professors. The study was conducted at UMass Amherst. The most surprising result, from my perspective, is that female associate professors are doing a great deal more service than their male colleagues, but that does not seem to be the case for assistant professors. I wonder, to what extent that may be an age/generational change, or is that only wishful thinking on my part?