Soror LG, we are so >>>>here<<<<.
You have a small, but decent African American population at USC. Factor in those who are too busy to pledge because they play sports. Those who want to pledge may not have the GPA. Then you have those who don't play sports. Some of them may find the other Greeks more tempting. Some don't want to pledge at all. That leaves very little guys who may be qualified and WANT to be Omega men.
The largest line I have ever seen for the fraternities at USC was 16 (and it wasn't the Omegas). The Omegas have to have 25 or more to accomplish the goal they are seeking. The Alphas had to have a line every semester to keep their numbers up for their house.
I also want PV06 to comment, since she's been out a shorter period of time than I have.