One of the myths about marriage most badly in need of busting is the idea that cohabiting before marriage makes you less likely to divorce – a sort of “try before you buy” effect.

This sounds quite sensible on the face of it. Then you look at the evidence and realise that the reality is very different.

Cohabitation before marriage either increases the rate of marital breakup or at best does nothing to reduce it. But tell this to most people and they’ll just give you a weird look, and I don’t really blame them – the evidence points to a conclusion that’s quite counterintuitive.

Over at the Institute For Family Studies, Scott Stanley has a post explaining one of the reasons why cohabitation doesn’t seem to work as a strategy for happier marriages. It’s to do with inertia.

All other things being equal, if two people are sharing one address, they will have a harder time breaking up than a non-cohabiting couple, even if their relationship has serious weaknesses or problems. That is, cohabitation has more inertia than dating. When they move in together, many people increase their constraints for staying in a relationship, or raise the costs of ending it, before they have reached a mutual dedication to being in the relationship.

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The idea of inertia as it relates to cohabitation and marriage is a little scary. We believe that some people marry a partner they would not have married if they’d never moved in together. They got “inertialized”—they made it hard to break up—too soon. That’s why my colleague Galena Rhoades and I have predicted and found over and over again that couples who wait to cohabit until marriage or until they have clear, mutual plans to marry report, on average, more marital happiness, less conflict, more compatibility, and so forth. Those couples are less likely to be prematurely caught in inertia.

This is called ‘sliding not deciding’. In short, if you’re not sure you want to marry the person you’re dating, cohabitation makes it easier to drift into marriage without ever taking the plunge and making a real decision and commitment. And if you’re waiting to cohabit until you’ve already decided to get married, you might as well just… get married. If you’re making a life-long commitment, it’s best to go for it wholeheartedly.

I’ll leave you with Stanley’s concluding words:

Inertia is really not all that mysterious once people see it clearly. We all experience it in many ways in modern life. But a lot of people think it’s only an issue when it comes to marriage, not cohabitation. It’s actually everywhere. When it’s time to really commit to someone, it’s worth accepting that commitment requires making a choice to give up other choices. But too many people give up options before making a real choice.