http://daringfireball.net/misc/2011/07/u-texas.png
When I worked IT for my college, we saw a similar pattern amongst residential computer registrations - almost all of students' machines were laptops, and the majority of those were running OS X.
This might not have been such a big deal back in the day (once they graduated, they probably got a job that forced them to use a PC, and so they stuck with one), but the PC landscape is changing dramatically. Nowadays, it's a lot easier to mainline a Mac after graduating.