I don't understand people being in open relationships where they are not monogamous.  Why even BE in a relationship?
That is a great question.  To me, an "open" relationship sounds more like "no" relationship.  What say you?
I agree.  Open marriage relationship couples report high levels of marital satisfaction.  That is just twisted.
I don't accept that premise.  Do you happen to have the % of stats?  To me, polls or studies such as that are slanted to create "facts".  
No, what I have read just said "many couples."  They don't even know the origin of the term open relationship.  Had to be late 60's.
I agree with you.  "Many" is a subjective term.  Many could be 10.  Marriage itself is a committed and dedicated relationship.  That's the point.  I believe relationships need to be clear, not "open."
I just looked it up.  The concept DID begin in the 1970s.  My parents told me about a party with keys in bowl.  They left.