As the children of the baby boomers come of age, they're likely to continue the trend of deferring marriage while searching for a partner, says Mr. Coates. Analyst Robert Knight of the Family Research Council says that until people discover that living together has pitfalls, it won't wane in popularity. The Census Bureau finds that cohabiting is most popular in the 24-35 age group, with 1.6 million couples. Sixty percent of cohabitors live with someone who has never married. Single people live together because they are trying to find a partner and don't know a better way to do it, says Mr. Coates, the futurist.
Research finds live-in relationships are highly sexual.
Married couples, however, score higher when asked if the sex is emotionally and physically satisfying, says Mrs. Waite. Spouses invest more emotionally in each other, she explains. Only 1 in 10 couples are still cohabiting after five years, say University of Wisconsin professors Larry Bumpass and James Sweet. This compares with 30 percent of married couples who didn't live together first, say Messrs. Bumpass and Sweet. Cohabitors have higher levels of conflict and abuse, and the highest rates of severe domestic violence.