People care way too much about bullshyt like this instead of the actual end product, which is the music.
What I think happens is Kanye has people in the studio with him and they all collaborate on something, whether it be a slick one liner, help with delivering a certain line a certain way, maybe even giving input on a snare or a kick or some shyt.
I don't think it's just Ye walking into a studio to a stack of written raps and he goes right into the booth and spits them, like what most of the people in this thread think.
Kanye's too creative to just have people writing everything for him.