Okay, at most schools with NPC sororities (26 national sororities), they use a system in rush to maximize the number of bids issued and insure almost all who want bids receive bids (and with Wake having a 3% non-match, it sounds like they use the system). The system limits the invitations the top ranked houses (not based on looks but on number of members and whether the top bids from the prior year accepted the bids) can issues, ‘funneling’ those who are unlikely to receive a final bid to other houses. Say there are 10 houses and 1000 girls going through rush. All 1000 are invited to the first party and there will be 10 parties. The second round there will be say 7 parties, but the top house cannot invite 700, but maybe only 500. A house that didn’t do quite as well numbers wise the year before might be able to invite back all 1000, but the recruits can only go to 7 parties. If someone isn’t invited to #1 house, it is more likely she will accept the 7 invitations she does receive, thus giving another house another chance.
On the recruit’s part, the promise is if they accept the max number of invitation in each round, they WILL get a bid as long as she receives at least one invitation in each round. Say the number of parties is 10, then 7, then 5, then 3. If the recruit accepts all 10, then 6 (all invited to), then 4, then 2, the system is designed that she should get a bid to one of those last two. If she is invited to 7 but only accepts invitations to 3 of those, the guarantee is gone.
It is a little complicated but it is a system that works. The houses have to be open about who they want and not keep inviting people back who they aren’t planning of giving a bid and the PNM have to be open to all the houses.
The ranking of the houses, at least for this system, is based on their records in recruitment and how successful they are in having bids accepted, in initiating the pledges, in retaining their members. Things change over time too, and houses go up and down in numbers.
Most schools try to have enough spaces to have everyone who wants to join the opportunity. At most of the big schools, everyone doesn’t live in the houses even one year. At my chapter at a flagship, there are 77 spots in the house, but most pledge classes are 130+, so that means a few sophomores and the officers live in the house. Others live in houses or apartments in the area and eat at the house on Monday nights. One daughter at a flagship lived in her house for 2.5 years and the other daughter (private school) spent 4 years on campus and never lived at the sorority (didn’t want to). They are all different. Some campuses give each sorority a wing of a dorm, others have no housing at all. Indiana does have a problem and I’m not sure why they haven’t added more chapters because they have interest from their students.