Of course there is a Huge difference between Fraternities and Soroities, DA!
But demogarphics do play a large part in this picture.
What Organizations are strong in a particular Area of the Country, as I am sure there is no one Soroity or Fraternity for that matter that are strong. Of course, the Fraternitys are as there are more Chapters.
The majority of the Colleges are at about 10-15 % of the Student Population, correct? So, if a school has 13,000 students, then that means between ALL Greek Orgs that 1,300 people are members.
Take for example, My school, there are 6 Fraternitys and 3 Soroities on Campus. My Chapter LXA is having problems, SPE, just had a huge house cleaning, and PSK is relative new and still small. Two NHPC Groups, one a Fraternity and one a Soroity which have normaly been small! There used to be 2 each when I was there!
We are in the process of regrowing along with the PSK. Now SPE is in real trouble of being gone! So down to 5. This is with a Population of @ 6,500 students.
So what is the answer? Well as was said above, it is up to the Active Chapters to strive to grow and force New Organizations to come on Campus. The Stronger We are as a Greek Organized Unit, the better We Will all BE!

The more Greek influence on campus, the stronger We as All Greeks Become!
And Yes, The Heads of Our Organizations do meet and discuss things about Growth and The Betterment of All of the Greek Community!
LXA Has presented Awards to Fellow Greeks from Fraternities and Soroities in the Name Of LXA!
Why, because of the Fellowship on that level that does not seem to get down to the Chapter level!
This level is where it needs to start to keep Us Growing Over all!