WASHINGTON — A new study found that in 11 countries across the globe, cohabiting couples have more doubts about their relationship lasting and give less importance to their relationship than married couples do.

The 2018 “Global Family and Gender Survey” (GFGS) examined living situations in various countries. It found that among adults age 18-50 with children under the age of 18 living at home, married couples had more confidence in the lasting quality of their relationships than those who were unmarried but living togeher.

Across Anglosphere countries, participants who were cohabiting with their partners were significantly more likely, in the past year, to have had serious doubts that their relationship with their partner would last.

The greatest difference was found in the United States, where 36% of cohabiting couples indicated having had serious doubts, in contrast to only 17% of married couples.

In the United Kingdom, 39% of cohabiting couples doubted their relationship’s stability. In Australia, that number was 35%; in Canada and Ireland, 34%; and in France, 31%.

In South America, cohabiting parents were less likely to have relationship doubts, with the least likely being Argentina, where only 19% of cohabiting couples expressed doubt.

The smallest difference found was in France, where relationship confidence between married and cohabiting couples differed by only one percentage point.

In addition to relationship stability, the study also found that, overall, cohabiting parents were less likely to define their relationship as “more important than almost anything else in life” compared with responses from married couples, though the difference varies country to country.

In the U.S., 75% of married couples said their relationship is vital to them, while only 56% of cohabiting couples said the same.

In Australia, the difference in importance placed on a relationship between the cohabiting and married families was found to be 15 percentage points; and in Ireland in was 14. In the United Kingdom, their responses differed by 17%.

For every South American country, the survey found between nine and 12 percentage points’ difference, except for in Mexico, which had a difference of 23%, and in Argentina, which had a difference of 19.

The responses from France were again the closest, with 73% of married couples and 70% of cohabiting couples agreeing that their relationship was more important than almost anything else in their lives.

Run by the Institute for Family Studies/Wheatley Institution, the GFGS conducted 16,474 online interviews with adults ages 18-50 in the countries of France, Canada, Australia, Ireland, United Kingdom, US, Chile, Peru, Mexico, Colombia and Argentina.

The study brief, written by Wendy Wang and W. Bradford Wilcox, noted that “a growing number of children in developed countries today are being raised by parents who are living together but not married.”

“Differences in stability between cohabiting and married families are noteworthy because children are more likely to thrive in stable families.”

The survey also suggests, they said, “that one factor explaining the stability premium for family life associated with marriage is commitment. Specifically, this brief finds that married parents are more likely to attach greater importance to their relationship, compared to cohabiting parents.”