III. EVIDENCE FROM THE SOCIAL AND BIOLOGICAL SCIENCES

In the last forty years, society has conducted a vast family experiment, and the outcomes are increasingly coming to light via scientific investigations. While no single study is definitive, and there is room at the edges for debate about particular consequences of marriage, the clear preponderance of the evidence shows that intact, married families are superior-for adults and especially for children-to alternative family arrangements. A great deal of research now exists from the anthropological, sociological, psychological, and economic sciences demonstrating the empirical benefits of marriage.

In virtually every known human society, the institution of marriage has served and continues to serve three important public purposes. First, marriage is the institution through which societies seek to organize the bearing and rearing of children; it is particularly important in ensuring that children have the love and support of their father. Second, marriage provides direction, order, and stability to adult sexual unions and to their economic, social, and biological consequences. Third, marriage civilizes men, furnishing them with a sense of purpose, norms, and social status that orient their lives away from vice and toward virtue.⁵ Marriage achieves its myriad purposes through both social and biological means that are not easily replicated by the various alternatives to marriage. When marriage is strong, children and adults both tend to flourish; when marriage breaks down, every element of society suffers.

The Well-being of Children

The evidence linking the health of marriage to the welfare of children is clear. During the last two decades, a large body of social scientific research has emerged indicating that children do best when reared by their mothers and fathers in a married, intact family. A recent report by Child Trends, a nonpartisan research organization, summarized the new scholarly consensus on marriage this way: "[R]esearch clearly demonstrates that family structure matters for children, and the family structure that helps children the most is a family headed by two biological parents in a low-conflict marriage."⁶ Other recent reviews of the literature on marriage and the well-being of children, conducted by the Brookings Institution, the Woodrow Wilson School of Public and International Affairs at Princeton University, the Center for Law and Social Policy, and the Institute for American Values, have all come to similar conclusions.⁷

Marriage matters for children in myriad ways. We focus here on the educational, psychological, sexual, and behavioral consequences for children of family structure, beginning with education. Children reared in intact, married homes are significantly more likely to be involved in literacy activities (such as being read to by adults or learning to recognize letters) as preschool children, and to score higher in reading comprehension as fourth graders.⁸ School-aged children are approximately 30 percent less likely to cut class, be tardy, or miss school altogether.⁹ The cumulative effect of family structure on children's educational performance is most evident in high school graduation rates. Children reared in intact, married households are about twice as likely to graduate from high school, compared to children reared in single-parent or step-families. One study found that 37 percent of children born outside of marriage and 31 percent of children with divorced parents dropped out of high school, compared to 13 percent of children from intact families headed by a married mother and father.¹⁰

Marriage also plays a central role in fostering the emotional health of children. Children from stable, married families are significantly less likely to suffer from depression, anxiety, alcohol and drug abuse, and thoughts of suicide compared to children from divorced homes.¹¹ One recent study of the entire population of Swedish children found that Swedish boys and girls in two-parent homes were about 50 percent less likely to suffer from suicide attempts, alcohol and drug abuse, and serious psychiatric illnesses compared to children reared in single-parent homes.¹² A survey of the American literature on child well-being found that family structure was more consequential than poverty in predicting children's psychological and behavioral outcomes.¹³ In general, children who are reared by their own married mothers and fathers are much more likely to confront the world with a sense of hope, self-confidence, and self-control than children raised without an intact, married family.

Marriage is also important in connecting children to their biological fathers and grounding their familial identities. Research by Yale psychiatrist Kyle Pruett suggests that children conceived by artificial reproductive technologies (ART) and reared without fathers have an unmet "hunger for an abiding paternal presence"; his research parallels findings from the literature on divorce and single-parenthood.¹⁴ Pruett's work also suggests that children conceived by ART without known fathers have deep and disturbing questions about their biological and familial origins. These children do not know their fathers or their paternal kin, and they dislike living in a kind of biological and paternal limbo.¹⁵ By contrast, children who are reared by their married biological parents are more likely to have a secure sense of their own biological origins and familial identity.

Family structure, particularly the presence of a biological father, also plays a key role in influencing the sexual development, activity, and welfare of young girls. Teenage girls who grow up with a single mother or a stepfather are significantly more likely to experience early menstruation and sexual development, compared to girls reared in homes headed by a married mother and father.¹⁶ Partly as a consequence, girls reared in single-parent or step-families are much more likely to experience a teenage pregnancy and to have a child outside of wedlock than girls who are reared in an intact, married family.¹⁷ One study found that only 5 percent of girls who grew up in an intact family got pregnant as teenagers, compared to 10 percent of girls whose fathers left after they turned six, and 35 percent of girls whose fathers left when they were preschoolers.¹⁸ Research also suggests that girls are significantly more likely to be sexually abused if they are living outside of an intact, married home-in large part because girls have more contact with unrelated males if their mothers are unmarried, cohabiting, or residing in a stepfamily.¹⁹

Boys also benefit in unique ways from being reared within stable, married families. Research consistently finds that boys raised by their own fathers and mothers in an intact, married family are less likely to get in trouble than boys raised in other family situations. Boys raised outside of an intact family are more likely to have problems with aggression, attention deficit disorder, delinquency, and school suspensions, compared to boys raised in intact married families.²⁰ Some studies suggest that the negative behavioral consequences of marital breakdown are even more significant for boys than for girls. One study found that boys reared in single-parent and step-families were more than twice as likely to end up in prison, compared to boys reared in an intact family.²¹ Clearly, stable marriage and paternal role models are crucial for keeping boys from self-destructive and socially destructive behavior.

Virtually all of the studies cited here control for socioeconomic, demographic, and even genetic factors that might otherwise distort the relationship between family structure and child well-being. So, for instance, the link between family breakdown and crime is not an artifact of poverty among single parents.²² Moreover, the newest work on divorce follows adult twins and their children to separate out the unique effects of divorce itself from the potential role that genetic (and socioeconomic) factors might play in influencing children's outcomes. This research indicates that divorce has negative consequences for children's psychological and social welfare even after controlling for the genetic vulnerabilities of the parents who divorced.²³

Why, then, does the evidence link marriage to an impressive array of positive outcomes for children? Both social and biological mechanisms seem to account for the value of an intact marriage in children's lives. From a sociological perspective, marriage allows families to benefit from shared labor within the household, income streams from two parents, and the economic resources of two sets of kin.²⁴ A married mom and dad typically invest more time, affection, and oversight into parenting than does a single parent; as importantly, they tend to monitor and improve the parenting of one another, augmenting one another's strengths, balancing one another's weaknesses, and reducing the risk that a child will be abused or neglected by an exhausted or angry parent.²⁵ The trust and commitment associated with marriage also give a man and a woman a sense that they have a future together, as well as a future with their children. This horizon of commitment, in turn, motivates them to invest practically, emotionally, and financially at higher levels in their children than cohabiting or single parents.²⁶

Marriage is particularly important in binding fathers to their children. For men, marriage and fatherhood are a package deal. Because the father's role is more discretionary in our society (and every known human society) than the mother's role, it depends more on the normative expectations of and social supports provided to fathers by marriage. Marriage positions men to receive the regular encouragement, direction, and advice of the mother of his children, and encourages them to pay attention to that input.²⁷ Not surprisingly, cohabiting fathers are less practically and emotionally invested in their children than are married fathers.²⁸ Nonresidential fathers see their children much less often than do married, residential fathers, and their involvement is not consistently related to positive outcomes for children.²⁹ By contrast, married fathers can exercise an abiding, important, and positive influence on their children, and are especially likely to do so in a happy marriage.³⁰

Biology also matters. Studies suggest that men and women bring different strengths to the parenting enterprise, and that the biological relatedness of parents to their children has important consequences for the young, especially girls. Although there is a good deal of overlap in the talents that mothers and fathers bring to parenting, the evidence also suggests that there are crucial sex differences in parenting. Mothers are more sensitive to the cries, words, and gestures of infants, toddlers, and adolescents, and, partly as a consequence, they are better at providing physical and emotional nurture to their children.³¹ These special capacities of mothers seem to have deep biological underpinnings: during pregnancy and breastfeeding women experience high levels of the hormone peptide oxytocin, which fosters affiliative behaviors.³²

Fathers excel when it comes to providing discipline, ensuring safety, and challenging their children to embrace life's opportunities and confront life's difficulties. The greater physical size and strength of most fathers, along with the pitch and inflection of their voice and the directive character of their speaking, give them an advantage when it comes to discipline, an advantage that is particularly evident with boys, who are more likely to comply with their fathers' than their mothers' discipline.³³ Likewise, fathers are more likely than mothers to encourage their children to tackle difficult tasks, endure hardship without yielding, and seek out novel experiences.³⁴ These paternal strengths also have deep biological underpinnings: Fathers typically have higher levels of testosterone-a hormone associated with dominance and assertiveness-than do mothers.³⁵ Although the link between nature, nurture, and sex-specific parenting talents is undoubtedly complex, one cannot ignore the overwhelming evidence of sex differences in parenting-differences that marriage builds on to the advantage of children.

The biological relationship between parents and children also matters to the young. Studies suggest that biological parents invest more money and time in their offspring than do stepparents.³⁶ New research by University of Arizona psychologist Bruce Ellis also suggests that the physical presence of a biological father is important for the sexual development of girls. Specifically, he thinks that one reason that girls who live apart from their biological father develop sexually at an earlier age than girls who live with their biological father is that they are more likely to be exposed to the pheromones-biological chemicals that convey sexual information between persons-of unrelated males. He also finds that girls who are exposed to the presence of a mother's boyfriend or a stepfather reach puberty at an earlier age than girls who are raised by unpartnered single mothers.³⁷ There is clearly more research to be done in this area, but the data clearly suggest that one reason marriage is so valuable is that it helps to bind a child's biological parents to the child over the course of her life.

Sara McLanahan and Gary Sandefur, sociologists at Princeton and Wisconsin respectively, sum up the reasons that marriage matters for children in this way: "If we were asked to design a system for making sure that children's basic needs were met, we would probably come up with something quite similar to the two-parent ideal. Such a design, in theory, would not only ensure that children had access to the time and money of two adults, it also would provide a system of checks and balances that promoted quality parenting. The fact that both parents have a biological connection to the child would increase the likelihood that the parents would identify with the child and be willing to sacrifice for that child, and it would reduce the likelihood that either parent would abuse the child."³⁸ Over the past few decades, we have experimented with various alternatives to marriage, and the evidence is now clear: children raised in married, intact families generally do better in every area of life than those raised in various alternative family structures. Those who care about the well-being of children-as every citizen should- should care about the health of modern marriage.

The Well-being of Adults

While the most important benefits of marriage redound to children, marriage also has significant benefits for the adult men and women who enter into it. Both married men and women benefit financially, emotionally, physically, and socially from marriage. However, we must also note that there are often gender differences in the benefits of marriage, and that the benefits of marriage for women are more sensitive to the quality of marriage than are the benefits of marriage for men.

The financial advantages of marriage are clear. Married men and women are more likely to accumulate wealth and to own a home than unmarried adults, even compared to similarly situated cohabiting or single adults.³⁹ Married men earn between 10 and 40 percent more money than single men with similar professional and educational backgrounds.⁴⁰ Married women generally do not experience a marriage premium in their earnings, but this is because most women combine marriage with motherhood, which tends to depress women's earnings.⁴¹ The material benefits of marriage also extend to women from disadvantaged backgrounds, who are much less likely to fall into poverty if they get and stay married.⁴² In general, marriage allows couples to pool resources and share labor within the household. The commitment associated with marriage provides couples with a long-term outlook that allows them to invest together in housing and other long-term assets.⁴³ The norms of adult maturity associated with marriage encourage adults to spend and save in a more responsible fashion.⁴⁴

Marriage also promotes the physical and emotional health of men and women. Married adults have longer lives, less illness, greater happiness, and lower levels of depression and substance abuse than cohabiting and single adults. Spouses are more likely to encourage their partners to monitor their health and seek medical help if they are experiencing an illness.⁴⁵ The norms of adult maturity and fidelity associated with marriage encourage men and women to avoid unhealthy or risky behaviors-from promiscuous sex to heavy alcohol use.⁴⁶ The increased wealth and economic stability that come from being married enable married men and women to seek better medical care.⁴⁷ The emotional support furnished by most marriages reduces stress, and the stress hormones, that often cause ill health and mental illness.⁴⁸ Men are particularly apt to experience marriage-related gains in their life expectancy and overall health. Women also gain, but their marriage-related health benefits depend more on the quality of their marriages: women in low-quality marriages are more likely to experience health problems and psychological distress than single women, while good marriages give women an important psychological and physical boost.⁴⁹

Marriage also plays a crucial role in civilizing men. Married men are less likely to commit a crime, to be sexually promiscuous or unfaithful to a longtime partner, or to drink to excess.⁵⁰ They also attend church more often, spend more time with kin (and less time with friends), and work longer hours.⁵¹ One study, for instance, showed that only four percent of married men had been unfaithful in the past year-compared to 16 percent of cohabiting men and 37 percent of men in an ongoing sexual relationship with a woman.⁵² Longitudinal research by University of Virginia sociologist Steven Nock suggests that these effects are not an artifact of selection but rather a direct consequence of marriage. Nock tracked men over time as they transitioned from singlehood to marriage and found that men's behaviors actually changed in the wake of a marriage: after tying the knot, men worked harder, attended fewer bars, increased their church attendance, and spent more time with family members.⁵³ For many men, marriage is a rite of passage that introduces them fully into an adult world of responsibility and self-control.

But why does marriage play such a crucial role in civilizing men-in making them harder workers, more faithful mates, and more peaceable citizens? Part of the answer is sociological. The norms of trust, fidelity, sacrifice, and providership associated with marriage give men clear directions about how they should act toward their wives and children-norms that are not clearly applicable to non-marital relationships. A married man also gains status in the eyes of his wife, her family, their friends, and the larger community when they signal their intentions and their maturity by marrying.⁵⁴ Most men seek to maintain their social status by abiding by society's norms; a society that honors marriage will produce men who honor their wives and care for their children.

Biology also matters. Research on men, marriage, and testosterone finds that married men-especially married men with children-have more modest levels of testosterone than do single men. (Cohabiting men also have lower levels of testosterone than single men.) Long-term, stable, procreative relationships moderate men's testosterone levels.⁵⁵ Judging by the literature on testosterone, this would-in turn-make men less inclined to aggressive, promiscuous, and otherwise risky behavior.⁵⁶

Of course, marriage also matters in unique ways for women. When it comes to physical safety, married women are much less likely to be victims of violent crimes. For instance, a 1994 Justice Department report found that single and divorced women were more than four times more likely to be the victims of a violent crime, compared to married women.⁵⁷ Married women are also much less likely to be victimized by a partner than women in a cohabiting or sexually intimate dating relationship. One study found that 13 percent of cohabiting couples had arguments that got violent in the past year, compared to 4 percent of married couples.⁵⁸ Studies suggest that one reason women in nonmarital relationships are more likely to be victimized is that these relationships have higher rates of infidelity, and infidelity invites serious conflict between partners.⁵⁹ For most women, therefore, marriage is a safe harbor.

It is not just marital status but the very ideal of marriage that matters. Married persons who value marriage for its own sake-who oppose cohabitation, who think that marriage is for life, and who believe that it is best for children to be reared by a father and a mother as husband and wife-are significantly more likely to experience high-quality marriages, compared to married persons who are less committed to the institution of marriage.⁶⁰ Men and women with a normative commitment to the ideal of marriage are also more likely to spend time with one another and to sacrifice for their relationship.⁶¹ Other research indicates that such a commitment is particularly consequential for men: that is, men's devotion to their wife depends more on their normative commitment to the marriage ideal than does women's devotion to their husbands.⁶² Simply put, men and women who marry for life are more likely to experience a happy marriage than men and women who marry "so long as they both shall love."

What is clear is that marriage improves the lives of those men and women who accept its obligations, especially those who seek the economic, emotional, and health benefits of modern life. Perhaps some modern men do not believe they need to be domesticated or do not wish to be burdened with the duties of child-rearing; and perhaps some modern women do not believe they need the security that a good marriage uniquely offers or fear that family life will interfere with their careers. But the data suggest that such desires can sometimes lead men and women astray, and that those who embrace marriage live happier lives than those who seek a false freedom in bachelorhood, cohabitation, or divorce.

The Public Consequences of Marital Breakdown

The public consequences of the recent retreat from marriage are substantial. As the evidence shows, marital breakdown reduces the collective welfare of our children, strains our justice system, weakens civil society, and increases the size and scope of governmental power.

The numbers are indeed staggering. Every year in the United States, more than one million children see their parents divorce and 1.5 million children are born to unmarried mothers. The collective consequences of this family breakdown have been catastrophic, as demonstrated by myriad indicators of social well-being. Take child poverty. One recent Brookings survey indicates that the increase in child poverty in the U.S. since the 1970s is due almost entirely to declines in the percentage of children reared in married families, primarily because children in single-parent homes are much less likely to receive much material support from their fathers.⁶³

Or take adolescent well-being. Penn State sociologist Paul Amato estimated how adolescents would fare if our society had the same percentage of two-parent biological families as it did in 1960. His research indicates that this nation's adolescents would have 1.2 million fewer school suspensions, 1 million fewer acts of delinquency or violence, 746,587 fewer repeated grades, and 71,413 fewer suicides.⁶⁴ Similar estimates could be done for the collective effect of family breakdown on teen pregnancy, depression, and high school dropout rates. The bottom line is this: children have paid a heavy price for adult failures to get and stay married.

Public safety and our justice system have also been affected by the retreat from marriage. Even though crime rates have fallen in recent years, the percentage of the population in jail has continued to rise-from .9 percent of the population in 1980 to 2.4 percent in 2003, which amounts to more than 2 million men and women.⁶⁵ Public expenditures on criminal justice-police, courts, and prisons-rose more than 350 percent in the last 20 years, from $36 billion in 1982 to $167 billion in 2001.⁶⁶ Empirical research on family and crime strongly suggests that crime is driven in part by the breakdown of marriage. George Akerlof, a Nobel laureate in economics, argues that the crime increase in the 1970s and 1980s was linked to declines in the marriage rate among young working-class and poor men.⁶⁷ Harvard sociologist Robert Sampson concludes from his research on urban crime that murder and robbery rates are closely linked to family structure. In his words: "Family structure is one of the strongest, if not the strongest, predictor of variations in urban violence across cities in the United States."⁶⁸ The close empirical connection between family breakdown and crime suggests that increased spending on crime-fighting, imprisonment, and criminal justice in the United States over the last 40 years is largely the direct or indirect consequence of marital breakdown.

Public spending on social services has also risen dramatically since the 1960s, in large part because of increases in divorce and illegitimacy. Estimates vary regarding the costs to the taxpayer of family breakdown, but they clearly run into the many billions of dollars. One Brookings study found that the retreat from marriage was associated with an increase of $229 billion in welfare expenditures from 1970 to 1996.⁶⁹ Another study found that local, state, and federal governments spend $33 billion per year on the direct and indirect costs of divorce-from family court costs to child support enforcement to TANF and Medicaid.⁷⁰ Increases in divorce also mean that family judges and child support enforcement agencies play a deeply intrusive role in the lives of adults and children affected by divorce, setting the terms for custody, child visitation, and child support for more than a million adults and children every year. Clearly, when the family fails to govern itself, government steps in to pick up the pieces.

The link between the size and scope of the state and the health of marriage as an institution is made even more visible by looking at trends outside the United States. Countries with high rates of illegitimacy and divorce-such as Sweden and Denmark-spend much more money on welfare expenditures, as a percentage of their GDP, than countries with relatively low rates of illegitimacy and divorce-such as Spain and Japan.⁷¹ Although there has been no definitive comparative research on state expenditures and family structure, and other factors-such as religion and political culture-may confound this relationship, the correlation between the two is suggestive. Of course, we also suspect that the relationship between state size and family breakdown runs both ways. For instance, earlier research on Scandinavian countries by sociologists David Popenoe and Alan Wolfe suggests that increases in state spending are associated with declines in the strength of marriage and family.⁷² Taken together, the retreat from marriage seems to go hand in hand with more expensive and more intrusive government; family breakdown goes hand in hand with growing hardship in disadvantaged communities, making the call for still more government intervention even more irresistible. It is a pathological spiral, one that only a restoration of marriage can hope to reverse.

Four Threats to Marriage

Until forty years ago, marriage governed sex, procreation, and childrearing for the vast majority of adults. In recent years, marriage's hold on these three domains of social life has weakened, with serious negative consequences for society as a whole. Four developments-the sad effect of decoupling marriage, sex, procreation, and childbearing-are especially troubling: divorce, illegitimacy, cohabitation, and same-sex marriage.

Divorce. From 1960 to 2000, the divorce rate more than doubled in the United States-from about 20 percent to about 45 percent of all first marriages. (Note: the divorce rate has declined modestly since 1980.) The data suggests that approximately two-thirds of all divorces involving children break up low-conflict marriages where domestic violence or emotional abuse is not a factor in the divorce.⁷³ Unfortunately, these children seem to bear the heaviest burden from the divorce of their parents.⁷⁴ Children from broken homes are significantly more likely to divorce as adults, to experience marital problems, to suffer from mental illness and delinquency, to drop out of high school, to have poor relationships with one or both parents, and to have difficulty committing themselves to a relationship.⁷⁵ Furthermore, in most respects, remarriage is no help to children of divorce. Children who grow up in stepfamilies experience about the same levels of educational failure, teenage pregnancy, and criminal activity as children who remain in a single-parent family after a divorce.⁷⁶

Divorce is also associated with poverty, depression, substance abuse, and poor health among adults.⁷⁷ More broadly, widespread divorce poisons the larger culture of marriage, insofar as it sows distrust, insecurity, and a low-commitment mentality among married and unmarried adults.⁷⁸ Couples who take a permissive view of divorce are significantly less likely to invest themselves in their marriages and less likely to be happily married themselves.⁷⁹ For all these reasons, divorce threatens marriage, hurts children, and has had dire consequences for the nation as a whole.

Illegitimacy (non-marital child bearing). From 1960 to 2003, the percentage of children born out of wedlock rose from 5 to 35 percent.⁸⁰ Although growing numbers of children born out of wedlock are born into cohabiting unions-42 percent according to one recent estimate-most children born outside of marriage will spend the majority of their childhood in a single parent home, in part because the vast majority of cohabiting unions-even ones involving children-end in dissolution.⁸¹ The biggest problem with illegitimacy is that it typically denies children the opportunity to have two parents who are committed daily to their emotional and material welfare.⁸² As noted above, children raised in single-parent families without the benefit of a married mother and father are two to three times more likely to experience serious negative life outcomes such as imprisonment, depression, teenage pregnancy, and high school failure, compared to children from intact, married families-even after controlling for socioeconomic factors that might distort the relationship between family structure and child well-being.⁸³

Nonmarital childbearing also has negative consequences for men and women. Women who bear children outside of marriage are significantly more likely to experience poverty, to drop out of high school, and to have difficulty finding a good marriage partner, even when compared to women from similar socioeconomic backgrounds.⁸⁴ Men who father children outside of marriage are significantly more likely to experience educational failure, to earn less, and to have difficulty finding a good marriage partner, even after controlling for socioeconomic factors.⁸⁵ Taken together, the rise of illegitimacy has been disastrous for children and adults, men and women, individuals and society.

Cohabitation. Since the early 1970s, cohabitation has increased more than nine-fold in the United States, from 523,000 couples in 1970 to five million couples in 2004.⁸⁶ Recent estimates suggest that 40 percent of children will spend some time growing up with one or both parents in a cohabiting union.⁸⁷ The growth of cohabitation in the U.S. is an unwelcome development. Adults in cohabiting unions face higher rates of domestic violence, sexual infidelity, and instability, compared to couples in marital unions.⁸⁸ Most studies find that cohabiting couples who go on to marry also face a higher risk of divorce, compared to couples who marry without cohabiting (although the risk of divorce for couples who only cohabit after an engagement does not appear to be higher than for married couples who did not cohabit).⁸⁹ Cohabiting unions are typically weaker than marriages, and appear more likely to lead to poor relationship outcomes. Cohabitation does not entail the same level of moral and legal commitment as marriage; couples often do not agree about the status of their relationship; and cohabiting couples do not receive as much social support from friends and family for their relationship as do married couples.⁹⁰

Cohabiting unions are particularly risky for children. Children reared by cohabiting couples are more likely to engage in delinquent behavior, to be suspended from school, and to cheat in school, compared to children reared by a married mother and father.⁹¹ Children cohabiting with an unrelated adult male face dramatically higher risks of sexual or physical abuse, compared to children in intact, married families. For instance, one Missouri study found that preschool children living in households with unrelated adults (typically a mother's boyfriend) were nearly 50 times more likely to be killed than were children living with both biological parents.⁹² Children also suffer from the instability associated with cohabiting unions. Even when children are born into cohabiting households headed by both their biological parents, they are likely to see one of their parents depart from the relationship. One recent study found that 50 percent of children born to cohabiting couples see their parents break up by their fifth year, compared to just 15 percent of children born to a marital union.⁹³ For all these reasons, cohabiting unions are not a good alternative to marriage but a threat to marriage, and they surely do not provide a good environment for the rearing of children.

Same-Sex Marriage. Although the social scientific research on same-sex marriage is in its infancy, there are a number of reasons to be concerned about the consequences of redefining marriage to include same-sex relationships. First, no one can definitively say at this point how children are affected by being reared by same-sex couples. The current research on children reared by same-sex couples is inconclusive and underdeveloped-we do not yet have any large, long-term, longitudinal studies that can tell us much about how children are affected by being raised in a same-sex household.⁹⁴ Yet the larger empirical literature on child well-being suggests that the two sexes bring different talents to the parenting enterprise, and that children benefit from growing up with both their biological parents. This strongly suggests that children reared by same-sex parents will experience greater difficulties with their identity, sexuality, attachments to kin, and marital prospects as adults, among other things. But until more research is available, the jury is still out.

Yet there remain even deeper concerns about the institutional consequences of same-sex marriage for marriage itself. Same-sex marriage would further undercut the idea that procreation is intrinsically connected to marriage. It would undermine the idea that children need both a mother and a father, further weakening the societal norm that men should take responsibility for the children they beget. Finally, same-sex marriage would likely corrode marital norms of sexual fidelity, since gay marriage advocates and gay couples tend to downplay the importance of sexual fidelity in their definition of marriage. Surveys of men entering same-sex civil unions in Vermont indicate that 50 percent of them do not value sexual fidelity, and rates of sexual promiscuity are high among gay men.⁹⁵ For instance, Judith Stacey, professor of sociology at New York University and a leading advocate of gay marriage, hopes that same-sex marriage will promote a "pluralist expansion of the meaning, practice, and politics of family life in the United States" where "perhaps some might dare to question the dyadic limitations of Western marriage and seek some of the benefits of extended family life through small group marriages..."⁹⁶

Our concerns are only reinforced by the legalization of same-sex marriage in Belgium, Canada, the Netherlands, and Spain-and its legalization in the Commonwealth of Massachusetts. Same-sex marriage has taken hold in societies or regions with low rates of marriage and/or fertility.⁹⁷ For instance, Belgium, Canada, Massachusetts, the Netherlands, and Spain all have fertility rates well below the replacement level of 2.1 children per woman.⁹⁸ These are societies in which child-centered marriage has ceased to be the organizing principle of adult life. Seen in this light, same-sex marriage is both a consequence of and further stimulus to the abolition of marriage as the preferred vehicle for ordering sex, procreation, and childrearing in the West. While there are surely many unknowns, what we do know suggests that embracing same-sex marriage would further weaken marriage itself at the very moment when it needs to be most strengthened.