what determines a house's rank?

Imho... The top houses are the for the most part the ones that act like they are better than everyone else. Alpha phis mainly care about social status so they work hard to make sure they're "top" by getting pretty party girls. Pi phis don't have anymore pretty girls than many middle tier sororities. However, they party really hard and put out. Not many girls in the house have boyfriends. Some middle tier sororities like Theta, achio and axid are more of the girl next door type of sororities. Majority of the girls in these houses have boyfriends.... See the correlation? "bottom" tier sororities either have internal issues, recruitment issues, or rough personalities(one house in particular). There are so many beautiful wonderful girls in "bottom" tier sororities that are so sweet. The tier system is bs because it doesn't really mean any thing once you graduate. What does mean something? Your sisterhood bonds with your sisters. Hopefully pnms chose a house based on the girls and not the social status.