Sorority recruitment or rush is a process in which university undergraduate women join a sorority. It is a procedure that includes a number of themed rounds in which different events are included.[1][2] The rounds are followed by preference night and finally bid day in which a college student receives an invitation to join a certain sorority.[1][2] The recruitment process is different at all universities and different universities have different sororities, meaning not all schools have the same chapters.[2] Students are continually joining sororities more on college campuses as membership has gone up nationwide, growing more than 15 percent from 2008 to 2011, to 285,543 undergraduates, according to the National Panhellenic Conference, which represents 26 nationally recognized sororities.[3] The National Panhellenic Conference also has the task of regulating sorority recruitment. The sorority houses follow specific rules to avoid infractions like staying silent before the doors are opened to the house.[clarification needed] The week before and during recruitment, girls are not allowed to wear their Sororities Greek letters out of their sorority houses to avoid influencing a potential new member (PNM).[4]