Men and women who cohabit may expect different things from the relationship, says a new study that finds men are often less committed that women to the relationship and feel less sure it will last.

That pattern of less committed and unevenly committed is the subject of a new paper for the RAND Corporation by sociologists Michael Pollard and Kathleen Mullan Harris.

They wrote that 52 percent of cohabiting young men ages 18 to 26 are not "almost certain" their relationship is permanent, compared to 39 percent of their live-in female partners. And 41 percent of the men also say they are not "completely committed" to the relationship, according to an article in The Atlantic written by National Marriage Project director W. Bradford Wilcox. Among the females, 39 percent are unsure their relationships will last, and 26 percent say they are not "completely committed."

Married men and women are both "much less likely to exhibit the low levels of commitment characteristic of many cohabiting relationships today," Wilcox wrote.

Wilcox said study suggests several bits of advice for young adults who are thinking about cohabiting, if they hope for a future together: Talk about the future, get on the same page and don't slide into marriage. Wilcox pointed out that research by sociologists Scott Stanley and Galena Rhoades, which was reported in the New York Times last year, suggests sliding instead of deciding when it comes to marriage is more apt to end in divorce.

Rhoades, a senior researcher at the Center for Marital and Family Studies at the University of Denver, has long tracked relationship trends. In 2009, in a paper called "Sliding vs. Deciding in Relationships," she said that more than 86 percent of never-married Americans would like to marry someday. She also said that two-thirds of those who live together moved in before making any long-term plans. They "tend to slide into living together."

Cohabiting couples are twice as likely to break up compared to married couples, Wilcox told the Deseret News recently. “Marriage is an institution that is surrounded by legal, religious and cultural meanings that people tend to take more seriously.”

The issue is not just of concern to the couple, experts said. More than half of all births to American women under 30 were outside of marriage. And two-thirds of all births in America are to women under 30. Often, the woman is cohabiting at the time of birth.

That nonmarital birth trend raises child well-being concerns, according to Child Trends. Its 2012 report says, "There are several reasons to be concerned about the high level of nonmarital childbearing. Couples who have children outside of marriage are younger, less healthy and less educated than are married couples who have children. Children born outside of marriage tend to grow up with limited financial resources, to have less stability in their lives because their parents are more likely to split up and form new unions, and to have cognitive and behavioral problems such as aggression and depression."

Even when children live with both biological parents, as is often the case in cohabiting couples, the children of not-married parents "are more likely to be poor and to face multiple risks to their health and development," the report said.

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