Here's a section of the interview:
LOPEZ: I’m stuck on the practical, forgive me. But you recommend that cohabitating couples move out before they get married. Is that ever realistic? Or do couples just laugh at the suggestion?
MCMANUS: Given the fact that cohabitating couples are 50 percent more likely to divorce than those who remained apart, there is no more important step that could increase the couple’s odds of a lifelong marriage than separating before the wedding. Is it practical? You bet! Is it likely? No. Not without a supportive couple mentoring the premarital couple who make arguments based on data and psychology that is persuasive. We have persuaded some couples to separate, and others to at least move into separate bedrooms and stop having sex until the wedding. That discipline increases each person’s self-respect and respect for their partner.
This really surprised me, though there is no good reason why it should have as it fits completely consistently with what you might expect if the Bible's advice is true.
In the past if I've married cohabiting couples (generally speaking, non-christians who had decided that they wanted to get married in a church building) I've mentioned that God's ideal is marriage and not cohabitation, but not made much more of it than that except to point to the statistics that indicate that marriages without cohabitation have a better chance of survival. It has generally been in the context of encouraging them that their decision to get married is a good one because it actually makes explicit what they are promising to do and removes any ambiguity from their situation.
Whether for good reasons or not I've wimped out on making any suggestions about actively moving out and ceasing cohabitation before marriage, on the flawed reasoning that it's not advice that non-Christians would be interested in hearing and it would make no difference anyway.
But this article has made me think again.
(Thanks to Craig for putting me on to this, and also Tim Challies).