This Article argues that marriage is an economically efficient institution, designed and evolved to regulate incentive problems that arise between a man and a woman over the life cycle of procreation. As such, its social and legal characteristics will provide a poor match for the incentive problems that arise in the two distinctly different relationships of gay and lesbian couples. Forcing all three relationships to be covered by the same law will lead to a sub-optimal law for all three types of marriage.
"Marriage" is a word familiar to toddlers, and yet so complicated that most adults cannot articulate its real meaning. (1) Marriage is an institution. (2) It is a complex set of personal values, social norms, religious customs, and legal constraints that regulate a particular intimate human relation over a life span. (3) Families are organized around marriage, and marriage provides benefits to families in terms of survival and success. The source of these benefits springs from the incentives created by the rich fabric of characteristics laced throughout the formal and informal marital rules. Social norms on personal sacrifice within the context of marriage encourage husbands and wives to devote their lives and resources to each other and their children. Signaling, self-binding commitments, and third-party sanctions (to name a few) are part of the marriage incentives that encourage socially good behavior and punish socially bad behavior, which incentives are necessary because both husbands and wives often have private incentives at odds with the interests of the community and other family members.
Marriage has never been a static, monolithic institution. Over time, the roles of men and women within marriage have changed. Social views on multiple wives, interracial relations, and divorce have changed. Legal rules regulating everything from the treatment of children and division of property to the grounds for divorce have changed. Yet certain elements of the institution of marriage have remained relatively constant for centuries. (4) For instance, marriage has always entailed more than a mere "contract." Marriage involves not just a couple, but extended family members, non-blood relations, and impersonal third parties like the church, state, or tribe. Marriage has always required an intention for a life-long commitment. Marriage has always contained the expectation of fertility. Marriage has always been prohibited between siblings. Of course, until very recently, marriage was available only to heterosexual couples. (5) This Article argues that the best explanation for the evolution of some marriage characteristics while others do not change is that marriage is an institution uniquely equipped to handle incentive problems between a man and a woman over their full life cycle. (6)
To some people, the idea of same-sex marriage is a fundamental departure from other marital changes, while for others, it is a natural extension of changes begun long ago. Thus, where same-sex marriage begins is a matter of debate. Some proponents go back to the Old Testament relationship of David and Jonathan. Others start with the Enlightenment concept of freedom of choice in spouse, and the radical idea of the pursuit of happiness in marriage. (7) Still others start with legal changes. Holland, followed by Belgium and Canada, became the first modern nation to legalize same-sex marriages at the turn of this century. (8) Other jurisdictions (including, for example, Scandinavian countries, Vermont, and California) have developed various types of registered civil unions that recognize and give partial marital rights to same-sex couples, and these often occurred before the current court decisions and legislation on same-sex marriage. (9)
The ultimate political fate of same-sex marriage, what form it takes, and how it relates to traditional marriage are still undetermined issues. An enormous debate continues over the issue of same-sex marriage, even in countries where the basic premise has been accepted, like Canada, where the government passed formal legislation changing the legal definition of marriage in the summer of 2005. …