...measurably the happiest in the USA, which is generally a very good place for universities. It's a combination of factors:
Very small numbers.
Massive endowment relative to those numbers (bigger than Harvard).
Students get need blind full funding, pretty much.
Enlightened alcohol policy.
If you're a grad student, you are guaranteed full funding until you're done. And you get to TA for classes of seven (this is the case for mine right now). And you get to be an RA with some ease.