It seems that student-to-faculty ratios among undergraduate programs vary drastically from discipline to discipline. Political science and economics, in particular, are oversubscribed. Definitely one of the things I liked about being a philosophy major in college was that it was a relatively small department with a low student-faculty ratio. That preserved a nice island of intimacy around my coursework even amidst a fairly large and impersonal overall university.
Part of what you see with these ratios, I guess, is that colleges are relatively unresponsive to demand-side factors among students.