"About 78% of human societies are polygynous, in which some men marry more than one wife."
Murdock, George Peter. Ethnographic Atlas.
"Only 22% of societies are strictly monogamous. No modern societies are polyandrous, in which one woman marries several husbands (not counting extramarital sex, and a poor region of India and Tibet where women marry brothers because the work of several men is needed to provide resources to raise a family). Only 3% of mammal species in general are monogamous, although at least 15% of primate species are."
Insel, T.R., Winslow, J.T., Wang, X., Young, L.J. "Oxytocin, Vasopressin, and the Neuroendocrine Basis of Pair Bond Formation," in Vasopressin and Oxytocin: Molecular, Cellular, and Clinical Advances, (Plenum, 1998, ISBN 0-306-45928-0), p. 217.
(I stand corrected about polyandrous women)
"Men, on average, are better off in a monogamous society. All men have equal opportunities for a wife and family. It's ironic that men, whose sexuality is more polygynous than women's sexuality, are the beneficiaries of monogamy."
The above quotes and references were taken from: Monogamy and Polygamy
Monogamy is working REAL well.
Divorce Rate : Divorce Rate In America
Marriage and divorce rates: EU comparison, 2001: Social Trends 33
Here's one regarding Polygamy and Same-Sex marriage, but this quote is somewhat relative:
...their favorite arguments against same-sex marriage are useless against polygamy. “It changes the very definition of marriage!” (No: marriage historically has been polygamous more often than monogamous.) “The Bible condemns it!” (Really? Ever heard of King Solomon?) “It’s not open to procreation!” (Watch “Big Love” and get back to me.)
If there’s a good argument against polygamy, it’s likely to be a fairly complex public-policy argument having to do with marriage patterns, sexism, economics, and the like. Such arguments are as available to gay-marriage advocates as to gay-marriage opponents. So when gay-rights opponents ask me to explain why polygamy is wrong, I say to them, “You first.”
Good Response To Polygamy Argument Creative Destruction
You're up, if you find helpful opinion pieces that also have some factual background, add those as well.