Liam Lenten sent me this by Robert Frank on the economics of polygamy. The article examines who is harmed by polygamy.
A traditional argument is that it harms women, particularly younger women who may be coerced to enter such marriages. But that is an argument against forcing women into any marriage. What about women who accept polygamy? Some are harmed by facing more restricted choices - they may have to settle for polygamy as a second-best option if they seek a particular partner. But with fewer wives available women generally have greater bargaining power in selecting a mate thereby increasing their advantage.
Also, too, polygamy would benefit some men who would not only prefer multiple wives, but are able to attract them. But what about men who prefer monogamy? Permitting plural unions would create an imbalance of men over women among monogamists. With many formerly eligible women no longer available, male bargaining power would fall - as happened recently in China as a result of female infanticide - and many men would never marry. Thus the likely victims of polygamy are men
'This conclusion is reinforced if we take account of the costly, and mutually offsetting, jockeying for position associated with men's attempts to win the attention of scarce women'.The wastefulness of such 'positional arms races' is clear from nonhuman animal species examples. Many species are polygynous, so some males take more than one mate and males battle ferociously for access to females. Size often decides these battles, so males tend to be considerably larger than females in polygynous species. For example, bull elephant seals weigh more than 6,000 pounds whereas females weigh 1,500 pounds. Natural selection favored larger males because the winners of the long and bloody battles between males often command nearly exclusive sexual access to harems of more than 50 females.
But being bigger increases vulnerabity to sharks and other predators. Relative not absolute size, governs the outcomes of fights, so it would clearly be better if each male were only half as large. All fights would be resolved yet all males would be less vulnerable to predators. But male seals have no way of curtailing the positional arms race that makes them so big.
Permitting plural marriage in human societies would unleash analogous competition. With women in short supply, men would face even more intense pressure than they do now to get ahead economically, to spend even longer hours honing their abs. Yet no matter how hard each man strove, the same number would be destined not to marry.
Unlike other animals, human societies can employ laws to constrain such positional arms races. Laws against polygamy function as positional arms control agreements that make life less stressful for men. This explains their appeal to the male legislatures that enact them.
A further thought: In Islamic societies women often cannot voluntarily contract marriage arrangements. From a male perspective, such restrictions are necessary if polygamy is to be widespread - otherwise the bidding up of female bargaining power that Frank describes will occur. It is crucial for the Frank argument to go through that women be free to contract. If they can't their bargaining power, both inside and outside marriage, will be reduced and hence they will be worse-off. Men without partners will still be worse off.