Cohabitation without marriage — the changing norm

The trajectory of cohabitation in the United States is steep and almost monotonic. The Census recorded about 439,000 unmarried different-sex partner households in 1960. By 1980, that figure had crossed 1.5 million. By 2000, it was nearly 4 million. By 2020, roughly 8 million different-sex cohabiting couples plus several million same-sex partnerships. The percentage of adults who have ever cohabited has risen from under 10% in the early 1970s to over 70% in the most recent cohort surveys. The trajectory is similar in nearly every affluent society, with Northern European countries running about a decade ahead of the United States and Mediterranean and Asian countries running roughly a decade behind. The phenomenon is not American; it is modern.

Sassler and Miller's central finding in Cohabitation Nation is that the meaning of cohabitation has bifurcated by class. Middle-class cohabitors describe their living-together as a chosen prelude to marriage, with explicit conversations about timing, finances, and shared goals. Working-class cohabitors more often describe a gradual slide into shared housing prompted by practical circumstances — a lease ending, a job loss, a pregnancy — without explicit conversation about what the cohabitation means or where it leads. The class difference produces very different outcomes: middle-class cohabitors marry at high rates and produce relatively stable marriages; working-class cohabitors more often stay cohabiting indefinitely, with higher rates of partnership dissolution. The same behavior — cohabitation — has different consequences depending on the surrounding economic context.

A growing literature argues that marriage has become, in the United States and elsewhere, a class marker rather than a default. Marriage rates have fallen most steeply among those without college degrees; college-educated couples still marry at high rates, often after extended cohabitation. The data is consistent with what Cherlin and others call the "deinstitutionalization" of marriage: the loss of marriage as a near-universal expectation and its replacement by a status marker that signals economic readiness, family stability, and middle-class membership. Cohabitation has filled the space marriage used to occupy for the population priced out of the luxury version. The two-tier system has implications for children, for inheritance, for retirement security, that the policy discourse has not fully absorbed.

For three decades, sociologists puzzled over the finding that couples who cohabited before marriage had higher divorce rates than those who did not. Several explanations competed. The selection hypothesis held that cohabitors were systematically different from non-cohabitors in ways that predicted divorce. The inertia hypothesis, developed by Galena Rhoades and Scott Stanley, held that cohabitation produced a kind of relationship momentum that pushed some couples into marriages they would not otherwise have chosen, with predictable later instability. The expectations hypothesis held that cohabitation shifted attitudes toward marriage in ways that increased divorce risk. As cohabitation has become more universal, the effect has weakened in more recent cohorts, suggesting that selection was doing much of the work. The methodological lesson is broad: behaviors that have unusual practitioners have unusual effects partly because of who does them, and the effects can fade as the behaviors normalize.

Wendy Manning's research has pushed the field to recognize that cohabitation is not a single thing. Her typologies distinguish between cohabitation as a step toward marriage (typical of younger, more-educated couples), cohabitation as an alternative to marriage (typical of older couples, particularly those who have been through divorce), cohabitation as an alternative to being single (typical of lower-income groups, often more transient), and cohabitation as a step toward a non-marital long-term partnership (an increasingly common pattern in Northern European data). Each of these has different durations, different stability profiles, and different implications for any children. Policy responses that treat cohabitation as a single category miss the structural differences across types.

Pamela Smock's work has documented the gap between cohabitation's behavioral prevalence and its legal recognition. Across U.S. states, cohabitants face wildly inconsistent treatment in property division at dissolution, in inheritance when one partner dies intestate, in medical decision-making during incapacitation, in immigration sponsorship, in tax filing, in social security benefits. The patchwork produces specific harms — usually concentrated on the partner with fewer assets, often the female partner, often after long cohabitations in which the parties assumed they were protected. Smock's argument is not that cohabitation should be assimilated to marriage but that the legal system should develop coherent frameworks for the relationships it actually has, rather than continuing to assume the relationships it used to have.

France's Pacte civil de solidarité, introduced in 1999 as a same-sex partnership recognition that was quickly adopted overwhelmingly by different-sex couples, has become one of the most-studied alternative-partnership institutions. By the late 2010s, the number of PACS unions in France was roughly equal to the number of marriages. The PACS is lighter than marriage — easier to enter, easier to exit, with weaker default property rules — and its popularity suggests that there is significant demand for a partnership form that is more committed than cohabitation but less committed than marriage. The American experience has not produced an equivalent middle option, partly because the legal recognition of cohabitation has been pursued primarily through marriage equality rather than through new partnership forms.

A major shift in the past three decades is the rise of childbearing within cohabitation. In 1980, about 5% of U.S. births occurred to cohabiting unmarried couples; by 2020, the figure was about 25%. The trajectory is similar across most affluent societies. The shift has consequences: children born to cohabiting couples experience higher rates of parental separation than children born to married couples, and the parental separations are harder to manage legally because cohabitation produces fewer default protections than marriage. The non-resident parent after a cohabitation breakup faces different and often weaker custodial defaults than the equivalent parent after a divorce. The legal system is slowly adapting, but the gap remains significant.

Same-sex couples were de facto cohabitors long before marriage equality, often by necessity. The legal recognition of same-sex marriage in many jurisdictions since 2000 has produced a natural experiment: when offered marriage, same-sex couples have taken it up at varying rates, with many continuing to cohabit even when marriage was available. The pattern is similar to different-sex couples in many ways, suggesting that the preference for or against marriage is not centrally about sexual orientation but about something else — perhaps the cultural and economic position of the couple, perhaps individual temperament, perhaps the practical legal needs they happen to have. The same-sex case has provided a useful test of the difference between cohabitation and marriage, with the result suggesting that the difference matters less to many couples than the older discourse assumed.

A small but symptomatic problem: there is no good word for an unmarried adult life partner. "Boyfriend" and "girlfriend" sound adolescent for a forty-year-old. "Partner" is read as evasive or as same-sex coded. "Significant other" is bureaucratic. "Lover" overstates the bedroom dimension. "Common-law spouse" is technically inaccurate in jurisdictions that have abolished common-law marriage. The vocabulary problem is a symptom of the institutional problem: the relationship form is more developed than the language. People living together for thirty years still introduce each other with words that sound provisional. The language will eventually settle on something, but the current period of awkwardness is itself instructive about how recently the underlying shift happened.

A largely unexamined consequence of the cohabitation shift is what happens in old age. Spousal benefits in pensions, social security, and many private retirement systems are structured around marriage. Long-term cohabitants who never married may discover at retirement that they have no claim on each other's benefits, that one cannot make medical decisions for the other, that inheritance must be explicitly structured to avoid going to estranged biological family. The first large cohort of long-term cohabitors is now reaching retirement age, and the policy issues are surfacing more visibly. The likely outcome is that the law will slowly adjust, but the adjustment will lag the demographic reality by a generation or more.

The cohabitation shift is not over. The proportion of adult partnerships that are formalized through marriage will continue to decline; the proportion of adult-years spent in cohabiting relationships will continue to rise; the legal and cultural infrastructure around cohabitation will continue to develop, unevenly, in response. What is hard to see from inside the shift is what stable end-state it will reach. One possibility is that cohabitation becomes a recognized institution in its own right, with developed legal frameworks and cultural rituals, occupying the space between casual partnership and marriage as a permanent option. Another is that the distinction between cohabitation and marriage erodes entirely, leaving a single category of adult partnership with various legal scaffolding options. The trajectory is clear; the destination is not. What is certain is that the marriage-centric vocabulary of the prior century is inadequate to the partnership landscape of this one.

1. Sassler, Sharon, and Amanda Jayne Miller. Cohabitation Nation: Gender, Class, and the Remaking of Relationships. Oakland: University of California Press, 2017. 2. Manning, Wendy D., and Pamela J. Smock. "Measuring and Modeling Cohabitation: New Perspectives from Qualitative Data." Journal of Marriage and Family 67, no. 4 (2005): 989-1002. 3. Smock, Pamela J. "Cohabitation in the United States: An Appraisal of Research Themes, Findings, and Implications." Annual Review of Sociology 26 (2000): 1-20. 4. Cherlin, Andrew J. The Marriage-Go-Round: The State of Marriage and the Family in America Today. New York: Alfred A. Knopf, 2009. 5. Bumpass, Larry, and Hsien-Hen Lu. "Trends in Cohabitation and Implications for Children's Family Contexts in the United States." Population Studies 54, no. 1 (2000): 29-41. 6. Stanley, Scott M., Galena Kline Rhoades, and Howard J. Markman. "Sliding Versus Deciding: Inertia and the Premarital Cohabitation Effect." Family Relations 55, no. 4 (2006): 499-509. 7. Manning, Wendy D. "Cohabitation and Child Wellbeing." The Future of Children 25, no. 2 (2015): 51-66. 8. Kiernan, Kathleen. "Unmarried Cohabitation and Parenthood in Britain and Europe." Law & Policy 26, no. 1 (2004): 33-55. 9. Perelli-Harris, Brienna, and Nora Sánchez Gassen. "How Similar Are Cohabitation and Marriage? Legal Approaches to Cohabitation Across Western Europe." Population and Development Review 38, no. 3 (2012): 435-467. 10. Smock, Pamela J., Wendy D. Manning, and Meredith Porter. "'Everything's There Except Money': How Money Shapes Decisions to Marry Among Cohabitors." Journal of Marriage and Family 67, no. 3 (2005): 680-696. 11. Lichter, Daniel T., Zhenchao Qian, and Leanna M. Mellott. "Marriage or Dissolution? Union Transitions Among Poor Cohabiting Women." Demography 43, no. 2 (2006): 223-240. 12. Edin, Kathryn, and Maria Kefalas. Promises I Can Keep: Why Poor Women Put Motherhood Before Marriage. Berkeley: University of California Press, 2005.