Which residence has mostly first year students and which residence has mostly upper year students?

I believe both Keyes and Les Prince have a higher proportion of upper-year students, but upper-years can be in any residence. Each building has a majority of first-year students, though--only 20% of all residence spots are reserved for upper years.

A document from 1997 states that Bates is the only residence where graduate students can live; I'm not sure if this is still an occurrence.