What goes into sorority rankings?

Why are sororities ranked the way they are? There seem to be clear “top” and “bottom” houses, but I don’t see people explain their placements. Popularity? Involvement? Kindness? Superficial things? Frats make a bit more sense, as it tends to be based on parties, but since sororities can’t throw…?

I’m not much of a believer in rankings. Wherever a PNM feels most at home is their home, and every sorority (and frat) member deserves respect if they give respect. That being said, I can’t help but wonder.

If someone could list some of the “top” and “bottom” sororities and explain their rankings, that would help. Please and thank you