brook--
Basically, caps are imposed by campuses, not nationals. Caps are imposed to keep those sororities that are large from completely dominating a rush situation. Caps are set by the Panhellenic, along with the campus. Nationals usually then have a standard at which they view a chapter in good standing as X% of cap.
When it comes to cap and quota, all sororities may take quota in the formal recruitment period. Once formal recruitment is completed, organizations that have not reached the cap through that process may COB new members. Hope this helps
