Cohabitation is becoming a way of life in the United States. Whereas only about l8% of Americans had cohabitated before marriage in the early l970s, that figure today is over 50%. If we follow the example of France, where over 80% of couples live together before marriage, cohabitation will become an almost required part of the dating-mating-marriage sequence.

In many ways this is understandable. Cohabitation can be a good thing. People get to know each other’s daily habits and get a "behind the scenes" look at their partner’s moods and feelings. The passion and romance gets a chance to wear off a little, and partners can get a clearer picture of their spouse to be. Couples not only find out if they are sexually compatible but also see how much sexual attraction and frequency wane when sex isn’t a scarce resource. Unless you have moral objections, this sounds like a good plan, doesn’t it?

It can be. But there is hard evidence that the plan may have pitfalls. Studies show at least 50% of cohabiting couples do not go on to get married. What's more, of those who do, more than 50% later get a divorce. In other words, not only does cohabiting not help insure a relationship’s success, there may be some aspects of cohabiting that make a breakup more likely.

Some experts have suggested that if there is a higher probability of breakups in this group it is only because people who cohabit have more liberal ideas about marriage in the first place. Logically, then, they are more likely than other couples to refuse to stay when the relationship sours. By contrast, social conservatives would likely reject cohabitation because of moral or religious reasons, and they would also be more likely to think of their vows as inviolate no matter how bad the relationship becomes. Hence, they would logically have lower divorce statistics.

But there may be another contributor--one that we should all take seriously: There is something about living together that makes real commitment become more optional and makes marriage seem more like a continuation of cohabitation (with its easier exit standards) than like marriage (with its oath of commitment 'til death do us part').

Of course, cohabitation itself doesn't always offer an easy out. While living together lacks the permanence of marriage, it ties couples in an economic contract, making it much harder for them to end this type of alliance than a purely dating relationship. This may make a troubled relationship last longer than it should--which may have a serious downside, for example, if inertia delays having children to the point that fertility is on the decline.

Bottom line: If you just want to hang out for a while with someone or you are uncommitted and not really worried about whether or not this will turn into a lifelong relationship together, there’s nothing wrong with cohabitation. But if eventually you want vows, kids, fidelity, a future--then approach cohabitation cautiously. Do it for a while if you need to know whether you are compatible, but you should know the answer to that within a year or so. Long-term cohabitation, at least for many people, doesn’t seem to lead to happily-ever-after endings.