A new study suggests that couples who live together before marriage may be less likely to eventually marry than previously believed.

Only about 40 percent of cohabiting couples studied ended up marrying within four to seven years. And 42 percent of cohabiting couples disagreed about the future of their relationship, the study found.

Contrary to popular belief, the study's author said, men with the best economic prospects and couples who were the most similar were not more likely than others to marry after living together.

Overall, the study shows that living together is not necessarily a transitional period that leads to marriage, said Sharon Sassler, co-author of the study and assistant professor of sociology at The Ohio State University.

SURVEY Do you think living together makes a couple more likely to have a successful marriage? No, they often won't get married. No, because when they finally committ it's harder. Yes, living together helps make sure you're compatible. It makes no difference. Results  |  Disclaimer

"For growing numbers of couples, cohabitation is now becoming an alternative to marriage or being single," Sassler said. "Many couples seem to be living together longer without marrying or ending their relationship."

This new research is different from previous studies in several ways. For one, it included data from couples and not just one person in a relationship. Many studies of cohabiting couples use data from the National Survey of Families and Households, which interviewed Americans over age 19 in 1987 and 1988 (and their partners, if any) and then again four to seven years later. Responses to the second round of interviews provided information about marriages or breakups among the participants.

The new study used statistical techniques to make up for those who couldn't be found for the second part of the study, often those with less education and lower income.

They found that the "repaired" data suggests only 40 percent actually married.

Another key finding was that -- contrary to what some other studies have shown -- cohabiting men who earn the most money are actually less likely than others to marry.

"Men who earn the most are least likely to marry, but also are less likely to break up with their partners," Sassler said.

Another surprise was the couples who were the most alike -- those who shared religions, were near the same age, and had similar levels of education -- were not more likely to marry than couples with significant differences in background.

The factor that best predicted whether cohabiting couples married was consensus regarding definite marriage plans, but Sassler said such consensus was relatively rare.

Fewer than one-third of the couples concurred that they had definite plans to marry. Another 42 percent disagreed about the future of their relationship. Others either agreed they wouldn't marry or thought they would eventually marry.

"Our results indicate that couples who use cohabitation as a trial period to test compatibility are far less likely to marry than couples who agree that there are definite marriage plans and a specific wedding date," Sassler said.

Also contrary to popular belief, when there was disagreement about future plans among couples, it was men as often as women who were pushing to get married. Neither men nor women had more success than the other in persuading reluctant partners to marry.

Sassler said this study suggests that many of our views about cohabitation may need to be revised.

"The transition from cohabitation to marriage is very different from transitions from singlehood," she said. "There seem to be fewer couples than we believed who decide to get married and many who are satisfied just staying in the current relationship."

The study was partially supported by a grant from the National Institute on Aging. The results were published in the current issue of the journal Social Science Research.