Where does it say 51%?

This is from CPS's FAQ

"Membership is available only to those individuals (self-employed or employed by a professional imaging business), who play a direct role in the creation of moving or still images for third parties on a full-time basis and are legal residents of the 50 United States or the District of Columbia."

The description changed, it was worded differently a few years ago. It was a bit less descriptive and more open.