Say, Chicago Astronomy. That department got 100 applicants in 2007 (200 in 2009). Then Texas has 125 and Colorado has 132 (both in 2007). Meanwhile, a school like Princeton only got 56 applicants in 2007 and 70 in 2008. Why do schools like Princeton have so few applicants, compared to many of the other schools? I know the generic answer "because more students are interested about their research groups, and have heard about them". But I'd like to hear more specific answers/ideas, if people have any.