Is Cuckold and wife share really happen? if so which percentage you think? 10% or less? yes it can be varied but as per your idea majority of married cpls are cuckold or they live straight vanilla type living?
I think that occasional cheating or straying in a marriage or relationship happens quite often. I think an ongoing hotwife/cuckold situation is still rare, but becoming more common. Still, I would put it at about 1%.