Prefs = Bid?
 

I was just curious to what extent being asked back to prefs indicates your chances of getting a bid from that sorority... I had thought that being asked back to prefs is almost a definite bid, but it didn't seem that way at all this time around for a lot of my friends

Well, everybody at a pref party is supposed to be somewhere on the bid list but if a PNM is near the bottom of both sororities' lists, she could possibly even end up bidless after attending 2 prefs.

If you are asked to prefs, you will be somewhere on that house's bid list but you are not guaranteed a bid at that house. Most PNM's go to more than one house for prefs but they can only get one bid, so they can't be guaranteed a bid from more than one house.

And if a sorority has 2 pref parties with 40 girls at each party and quota is 50, well obviously they can't give bids to all the women.

I'll let the more knowledgeable among us give a more technical answer on bid matching.