drop rate

Can't wait to see if you get a response.

remember pledge classes get bigger each year so the amount of girls who drop really isn't as many as it would appear

It's a combination of things. Pledge classes keep getting bigger for one. Members drop out at some point. Sometimes they get expelled from the sorority for conduct issues or grade problems. Sometimes they get expelled from school for grades. Members transfer to other schools. And a lot of girls just drop out of college at some point, but especially after freshman year.

actives i know of that drop out usually just get so busy with their major (like nursing kills them) and other things (like significant others not in greek system) and it becomes not worth the money and time--especially if they were never totally into it anyway.

There are a lot of girls that graduate early, who study abroad senior year, or who have already left for a job by the time graduation happens.

In 2011, (the senior class that just graduated) had 75 in their pledge class. So that just goes to show you how much bigger they've gotten every year.

140 in a class?
Gamma Phi Beta's about the only one that's had that big a class in past years.
This year might be different.
A certain percentage always resigns - financial reasons, grades, boyfriends, drama, etc. - crap happens. And a certain percentage are still members, but transfer to different schools, take a year or two off, get married, take a job, whatever.
A steep drop from freshman to senior years is normal. That's true not just for Greeks but for overall enrollment.
Leaving school early does not mean the end of your sorority membership, though. Just the beginning of the rest of your sorority life - alumnae status. That's one of the nicest things about being a sorority member.