I talked to Ballerina until real late last night and she said that quota was 25 and that 180 girls started out in rush. Since there are 6 sororities, 25 x 6= 150...but I heard that all but one made quota. Therefore, that's a lot of girls who went bidless.
I'm told that Valdosta has a lot of PNMs who will only accept one sorority (it varies with the girl) and that has a lot to do with the dropout rate.
*still floating with happiness because all my college girls are Greek!*