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By Scott M. Stanley and Galena K. Rhoades

The CDC’s National Center for Health Statistics (NCHS) put out a report in May on the demographics of cohabitation, with interesting contrasts among adults who are cohabiting, married, or neither. The report is based on a large, representative national survey of U.S. adults aged 18 to 44, sampled between 2011 and 2015. To conduct the analyses, the authors (Nugent and Daugherty) selected only adults who had sexual intercourse with a partner of the opposite . They did that to ensure the groups were comparable in some respects regarding their histories in intimate relationships. The groups reflect those who were currently cohabiting, married, or neither at the time of being surveyed.

Cohabitation, , or Neither

The report shows that, as of 2015:

17.1 percent of women and 15.9 percent of men were cohabiting.

44.9 percent of women and 43.5 percent of men were married.

38.0 percent of women and 40.6 percent of men were unmarried and not cohabiting.

This type of data does not address pathways over time, such as how many among the current cohabiters will eventually marry, or how many of those not currently residing with a partner will eventually do either or neither. However, the data do provide estimates of the number of times people in the groups had cohabited outside of marriage, up to the time they were surveyed.

Sixty-seven percent (67 percent) of those currently married had cohabited before marriage with one or more partners.[i] Many of those currently unmarried or not cohabiting had cohabited before. Fifty-one (51.4 percent) of the women in that group had lived with one or more partners before, and 42.9 percent of the men had done likewise. Doing a little math, we estimate from the report that 64.5 percent of the entire sample has cohabited with a romantic partner at some point outside of marriage. That’s not the percent of people sampled who will cohabit outside of marriage at some point in their lives, though. The lifetime percent for this group would, of course, be higher. To get that number, you’d have to follow everyone in the sample until each person had either cohabited or died. That could be a long wait. (It might be that Facebook could eventually tell us those numbers.)

The data on premarital cohabitation history in this sample will be an underestimate, because the marrieds make up a higher percentage of the older people in that age range, and there is every reason to believe that the youngest non-marrieds in the sample are more likely to cohabit prior to marriage than those who are older. Other estimates not based on this specific report are that the percentage of people living together before tying the knot is now at an all-time high of over 70 percent.[ii] We believe this figure will go higher still. There remain some groups, particularly the more traditionally religious,[iii] who will not live together before marriage, but otherwise, cohabitation is common, and there is little stigma associated with it.

Thus, a very high percentage of people in the U.S. cohabit outside of marriage. It is now normative behavior. Wendy Manning has estimated that, “The percentage of women ages 19-44 who have ever cohabited has increased by 82 percent over the past 23 years.” For those aged 30-34 in 2009-10, she has shown that 73 percent of women had already cohabited with someone. If you combine such numbers with the fact that, as Susan Brown has shown, there is a steady increase in cohabitation among older adults (after the death of a spouse or ),[iv] it is easy to imagine that the number of people who will eventually cohabit outside of marriage could reach 80 percent or more.

Cohabitation has greatly increased, in large measure because while people are delaying marriage to ever greater ages, they are not delaying sex, living together, or childbearing. In fact, on the latter point, Manning noted in her recent address to the Population Association of America that almost all of the increase in non-marital births in the U.S. since 1980 has taken place in the context of cohabiting unions.

Cohabiting with more than one partner outside of marriage has also gone steadily higher.[v] The NCHS report does not demonstrate the trend, but the data reported do show that 44 percent of the currently cohabiting group and 20 percent of the neither cohabiting nor married group has already lived with two or more partners. Ever higher levels of serial cohabitation mean that more people are on one of the pathways strongly associated with risks for family instability or divorce.[vi]

Prior research has shown that serial cohabitation is strongly associated with economic disadvantage among unmarried couples,[vii] lower odds of marriage, and increased odds of poor marital outcomes, but serial cohabitation is growing rapidly among different population groups.[viii]

Increasing rates of cohabitation as well as serial cohabitation might be of no special consequence except for the point noted above: that many births now occur in cohabiting unions. Some percentage of these couples have a long-term commitment similar to marriage, but on average, cohabiting parents are much more likely than married parents to break up,[ix] resulting in increasing odds of family instability for children. Much of this risk is due to selection, a subject we will come to below.

Other Characteristics of These Groups

Other findings from the NCHS report are consistent with the way that basic family patterns have increasingly diverged around cultural, educational, and economic lines. For example:

47.9 percent of cohabiting women had household incomes less than 150 percent of the federal poverty line, compared to 25.6 percent of married women.

36.1 percent of cohabiting men had incomes less than 150 percent of the federal poverty line, compared to 21.2 percent of married men.

25.2 percent cohabiting women had incomes over 300 percent of the federal poverty line, compared to 48.1 percent of marrieds.

32.4 percent of cohabiting men had incomes over 300 percent of the federal poverty line, compared to 52.4 percent of marrieds.

This is one of the more striking examples of the fact that a lot of cohabiting women and men tend to be poor compared to married women and men. The data on follow the same pattern, of course. Married people had the most education, followed by those who are not married or cohabiting, with cohabiting people reporting lower levels of education than the other two groups. For example:

25.3 percent of cohabiting women had a bachelor’s degree compared to 43 percentof married women.

16.2 percent of cohabiting men had a bachelor’s degree compared to 36.5 percent of married men.

While the education levels of many of the cohabiters in this sample will go higher over time, the findings from many studies show that cohabitation (particularly with cohabiting relationships not leading directly to marriage) is associated with being more disadvantaged, on average.[x] The data are consistent with the story of a class divide around marriage and cohabitation.[xi]

Attitudes and Experiences

This NCHS report also presents differences in the three groups based on attitudes and experiences about unmarried sex, cohabitation, and having children outside of marriage. Not surprisingly, both of the non-married groups are less traditional in their views than those who are married. These findings are reflected in the table below from the report.

While there are clear differences, large majorities of every group believe that having and raising children without being married is fine; this is endorsed by the greatest number of cohabiters. Of course, that finding would have been quite different decades ago. Marrieds are the most disapproving of cohabitation outside of marriage, but even most of the married group agreed that it is all right to do so.

Source: CDC. Public Domain

Majorities of every group also believe that living together before marriage may help prevent divorce. This is of particular interest to us given our research related to this question.[xii] The percentage believing this was highest for those currently cohabiting.

This notion has had wide acceptance since at least the mid-1990s, when three-fifths of high school students believed that, “It is usually a good idea for a couple to live together before getting married in order to find out whether they really get along.”[xiii] It is worth noting that there is virtually no evidence in support of this belief. However, it is also fair to note that there used be a lot clearer evidence to the contrary.

Regardless, we believe that there is considerable evidence that some patterns of living together before marriage are associated with increased risks for less successful marriages. We do think experiences and choices matter for future outcomes. This assertion is mildly controversial among those who study cohabitation. To be sure, there is a mountain of evidence for selection in both who cohabits and who will cohabit in the riskier ways. What that means is that people who are already at greater risk for worse outcomes in relationships, because of things like family background, disadvantage, or individual vulnerabilities, are also more likely to do any of the following: cohabit and not marry, cohabit before having clear, mutual plans to marry, or cohabit with a number of different partners over time. There is plenty of evidence of other patterns in the NCHS report related to cohabiters being more select for various relationship risks. Consider the following findings.

Relationship Risks Associated with Cohabitation

Cohabiters were more likely (74 percent) than those currently married (56 percent) to have had sexual intercourse before the age of 18. Cohabiting women were also more likely to report ever having an unintended birth (43.5 percent) compared to married women (23.9 percent). These types of patterns are associated with life-long risk factors already present in the lives of many people. Of course, you could argue that such differences also reflect choices people make that have potentially causal, life-altering consequences. Such debates are endless, but we do not doubt a huge role for selection in all of this. And yet, we believe there often are causal elements impacting life outcomes related to the experience of cohabitation.

First, it has been shown that cumulative cohabiting experience changes peoples’ beliefs about marriage.[xiv] While that research is older, the theory behind the research is compelling. Much research shows we learn from experiences, and experiences change our beliefs. We believe that the increase in cohabitation, serial cohabitation, and premarital cohabitation has led to consistent downward trends in belief that marriage is special.

Second, cohabitation makes it harder to break up, net of everything else. Because of the inertia of living together, some people get stuck longer than they otherwise would in relationships they might have left or left sooner. In fact, we believe some people marry someone they would otherwise have left, because cohabitation made it too hard to move on. Inertia should be the greatest problem for couples who had not decided beforehand on their future, such as by already having mutual plans to marry (e. ., engagement) or, of course, by first marrying. While the increased risk can be modest, the prediction is consistently supported with at least seven reports using six different samples, showing that those who start cohabiting before deciding to marry report lower average marital quality and are more likely to divorce.[xv] This added risk is compounded by the fact that most couples slide into cohabiting, rather than make clear decisions about what it means and what their futures may hold.[xvi]

Third, cohabitation is increasingly a context for childbearing. Since cohabiting parental unions are relatively unstable, the increasing number of couples who break up in such unions will mean more people entering future relationships with the challenge of children in tow.

Evidence of selection abounds, but so do reasons for believing that experiences and personal choices are relevant to life outcomes.

Complexity Abounds

These ever-changing patterns in relationship and family development are complex, and they do not operate in the same way for all. For example, there is research suggesting that cohabiting experiences may lead to more positive attitudes about marriage among young, African American adults. More broadly, as Sharon Sassler and Amanda Miller argue in Cohabitation Nation, there are various social class disparities that impact things like if and how soon a person will move in with a partner. Some pathways will lead to different sets of outcomes for different people, and some people have more ability (economic and personal) to avoid paths that increase the odds of poor outcomes.[xvii]

The extraordinary changes of the past four decades reflect how ordinary cohabitation has become. There is no a simple story here, only an ever-unfolding one of increasingly complex families.

This article first appeared on the blog of the Institute for Family Studies on June 20, 2018.