Social science data indicate that the intact family-defined as a man and a woman who marry, conceive, and raise their children together-best ensures the current and future welfare of children and society when compared with other common forms of households. As alternative family forms have become more prevalent since the 1960s, social science research and government surveys have indicated an accompanying rise in a number of serious social problems.

Government's interest in marriage has been based primarily on its interest in the welfare of the next generation. Among the many types of social relationships, marriage has always had a special place in all legal traditions, our own included, because it is the essential foundation of the intact family, and no other family form has been able to provide a commensurate level of social security.

In all other common family and household forms, the risk of negative individual outcomes and family disintegration is much greater, increasing the risk of dependence on state services. A free society requires a critical mass of individuals in stable households who are not dependent on the state. The most stable and secure household, the available research shows, is the intact family. Therefore, the state has an interest in protecting the intact family and we should be cautious about facilitating other forms of household, the effects of which are either deleterious or unknown.

Compared with counterparts in other common household arrangements, adolescents in intact families have better health, are less likely to be depressed, are less likely to repeat a grade in school, and have fewer developmental problems, data show. By contrast, national surveys reveal that, as a group, children in other family forms studied are more likely to experience poverty, abuse, behavioral and emotional problems, lower academic achievement, and drug use. These surveys illustrate

• Adolescents in intact families, as a group, are the least likely to feel depressed compared to those with divorced, step-, cohabiting, or single parents; (National Longitudinal Survey of Adolescent Health)
• The national average grade-point scores of children in intact families is 2.98, compared to 2.79 for children of cohabiting parents and 2.71 for children living in stepfamilies; (National Longitudinal Survey of Adolescent Health)
• The rate of youth incarceration is significantly greater for children raised in single-mother and stepfamily homes than for those raised in intact families, even after controlling for parental income and education; (National Longitudinal Survey of Youth)
• Children in non-intact families are three times as likely to have children outside of marriage; (National Longitudinal Survey of Youth.) and
• Rates of engaging in problem behaviors such as lying, stealing, drunkenness, and violence are sharply higher for children of divorce compared to children in intact families. (National Longitudinal Survey of Adolescent Health)

During the 1990s, a serious public policy debate resulted when emerging social science data showed the consequences of several decades of experimentation with family forms. Out of this increased awareness grew a movement for policy and cultural changes to reinforce and restore marriage in America. Policy decisions-such as welfare reform-were grounded in these data. We have seen some of the fruit of those efforts in declining rates of teen sex and childbearing.

By contrast, the current debate over same-sex marriage is not anchored in sound research, and data on the consequences of children being brought up by same-sex couples remains scarce. Same-sex couples with children constitute a new form of household that has not been carefully studied. Nor has the objective of this policy discussion been clearly defined as the interest of children or the future of the nation's families.

Same-sex marriage advocates propose that we institutionalize a social experiment in its early stages by elevating it in law to the status of the oldest of institutions: marriage. That experiment is the same-sex coupling and parenting recently taking place around us. To be sure, Americans have become more accepting of other types of sexual experimentation-sex outside of marriage, cohabitation, single parenting-but do not equate them with or see them as a substitute for marriage. None of these experiments has been regarded in law as the equivalent of the intact family. Yet this is precisely the proposal before us on the question of same-sex marriage: that we institutionalize in law an experiment about which we have very little knowledge.

The data on the homosexual household is extremely limited. We know relatively little about the long-term effects of homosexual relationships on partners and even less about the children that will be raised in such households. Such an absence of data should give us pause before reconfiguring the basic institution of society. Thus we should study the results of the current experiment in homosexual households with children rather than forcing communities at large to accept, by law, same-sex marriage and parenting.

We should also further explore what it is about marriage that sets the intact family apart in the current research . Many would contend that the unique natures and contributions of a male and a female constitute the critical characteristic of marriage, and that the distinctive sexual nature and identity of each parent, along with their number (two rather than one) and relationship status (marriage rather than cohabitation), gives the intact family the exceptional quality it exhibits. This needs to be examined carefully, to determine how having two parents of opposite sexes contributes to the upbringing of a child.

In the meantime, with the policy debate forced by same-sex marriage advocates beyond the conclusions of existent social science research, we must look to the best evidence currently available about family forms and their social impacts. What we know about alternative family forms is a good indicator of what we might expect from this variant.

Modern policymaking should be informed by the realities of available empirical evidence. In time, the data will be forthcoming on this newest form of experimentation, same-sex partnering and parenting, and its effects on homosexual men and women and on those who live with them. In the meantime America's marriage and family law should stay the course based on what we do know.

Jennifer Marshall is Director of Domestic Policy Studies at The Heritage Foundation.