There have been a few threads on this. I posted in one of them about the break down of number of chapters by conference (NPC, NIC, NPHC, etc), but I can't find it. I think U of I is largest in terms of number of chapters. I think other schools have higher percentages and higher number of members.
And that's Northwestern's logo next to the highest percentage of Greeks in the Big Ten, not Penn State.
ETA: Here it is:
http://www.greekchat.com/gcforums/sh...3&postcount=46
And yes, my count of 36 sororities is correct. The DI is wrong. Because 59 + 39 =/= 95.
