You won’t be surprised to learn that cohabitation, or ‘shacking up,’ has skyrocketed in the U.S. Specifically, it has increased over the past half century by more than 1,500 percent.

‘Living in sin’ is in vogue. But that doesn’t mean it’s smart.

Many people say they shack up for economic reasons, but the research shows most couples do so in order to test the waters. This is especially true for those who are products of divorce and don’t trust marriage as an institution. They think living together will help their chances of success. It won’t.

There is zero evidence that ‘shacking up’ is helpful to marital happiness or longevity. There is, however, plenty of evidence that it’s harmful.

One

For one thing, shacking up is linked to lower levels of commitment and increased likelihood of divorce.

Two

Women are far more likely to view cohabitation as a step toward marriage, while men are more likely to see it as a way to test a relationship or to postpone commitment. This gender asymmetry is associated with negative interactions and lower levels of commitment, which makes sense since the partners clearly aren’t on the same page.

Three

Shacking up doesn’t allow for the objectivity couples need in trying to determine whether or not they should marry. Instead, they get in deeper and deeper until they can’t see the forest for the trees. As a result, they end up “sliding” into marriage rather than “deciding” to marry. Living in separate spaces makes it easier to make a well-thought-out decision.

Four

But the greatest problem with shacking up is the one we never talk about: the psychological toll that moving in with someone, only to later move out, takes. It may be logistically easier to separate after shacking up than it is after getting divorced, but the emotional baggage people carry with them into their new relationship is often no less significant than had they gotten a divorce. And if you’ve had multiple living partners, you can multiply the baggage.

It’s like getting divorced several times over. The ability to trust diminishes with each broken relationship, often until one’s ability to trust has been completely shattered. It can also do considerable damage to a woman’s self-worth.

Five

There’s also the fact that lack of commitment makes most women uneasy. A woman’s need for emotional security is more pronounced than a man’s; so no matter how content a woman may appear to be in a co-habitating relationship, deep down what she really wants is a ring.

There’s just no upside to cohabitation. At the very least it will take up valuable time that could otherwise be spent dating marriage-minded men. I can’t tell you the number of women I hear from who’ve wasted years of their lives living with men who will never commit to them. Don’t be that woman! If all of this isn’t convincing enough, there’s this: you have a biological clock, and your boyfriend does not.

That means shacking up benefits him, not you, since you will potentially waste x number of years hoping, but not knowing, if the relationship will work out. Then you’ll feel the clock ticking and begin to inquire whether or not he plans to marry you. If he refuses, you’re back to the drawing board at a very late age. And that’s not a place you want to be.

For all of these reasons, your best chance at lasting love is to establish a relationship while living in your own apartment—that way you’re not locked in. In the past, that was called dating. And it works.