Cohabitation is the snake in grass which is diverting tens of millions of Americans from marrying, and is increasing the likelihood of divorce for those who marry after living together.

My wife and I wrote the definitive book on this subject, Living Together: Myths, Risks & Answers. Today's generation of young adults has bought the idea that it makes sense to test the possibility of marriage by living together. That's the biggest myth of all. However, as one marriage educator put it: "You can't practice permanence." Two sets of data prove she's right.

First, according to the latest Census data, 7.6 million couples cohabited in 2011 - an 18-fold hike since 1960 when 430,000 couples were living together. Clergy tell me that two-thirds of those coming to marry, are cohabiting. If so, that's 1.5 million of the 2.2 million who married last year.

What happened to the other 6.1 million cohabiting couples? Some continued living together, but most broke up, undergoing the pain of a "premarital divorce," as we put it.

That is such a searing experience - particularly for women - that tens of millions never do marry. The number of never-married Americans has jumped from 21 million in 1970 to 63 million - a tripling while population grew only about 50 percent.

The result is that only 51% of American adults are married today, down from 72% before cohabitation diverted millions from marriage. The Pope rightly expressed concern about the "decrease in the number of young people who approach the sacrament of matrimony."

Secondly, those who cohabit and then marry are MORE likely to divorce, 61% more apt to divorce, reports a Penn State study by Dr. Paul Amato.

The Pope's proposed solutions are also on target: better "preaching" and better "marriage preparation programs."

When was the last time you heard a sermon on the danger of cohabitation? I bet never. I have asked hundreds of pastors, "Have you ever preached on cohabitation?" Only one hand in 50 goes up. Why not give a copy of this column to your pastor, with hard data on the harm of living together, which underscores the wisdom of Scripture.

St. Paul wrote, "Flee fornication," in I Cor. 6:18. "All other sins a man commits are outside his body, but he who sins sexually sins against his own body. Do you not know your body is a temple of the Holy Spirit?"

Pope Benedict told the bishops, "There is an urgent need for the entire Christian community to recover an appreciation of the virtue of chastity. The integrating and liberating function of this virtue should be emphasized by a formation of the heart, which presents the Christian understanding of sexuality as a source of genuine freedom, happiness, and the fulfillment of our fundamental and innate human vocation to love." But only in marriage. In our book Living Together, we offer three other answers:

1. Require those getting married to take a premarital inventory such as PREPARE-ENRICH which asks the man and woman whether they agree or disagree with 150+ statements:

* When we are having a problem, my partner often refuses to talk about it.
* Sometimes I wish my partner were more careful about spending money.

2. Train mature couples in healthy marriages to be Mentor Couples who review every issue on the Inventory with the couple over 5-6 sessions, and teach communication and conflict resolution skills.

3. Join with other churches of all denominations in a city to create a Community Marriage Policy in which all agree to make marriage a priority by requiring the taking of an inventory, and reviewing it with trained Mentors. Churches also agree to hold an annual marriage enrichment event to strengthen existing marriages, to help couples in crisis to succeed, to reconcile separated couples, and help those in stepfamilies be successful.

An independent study by the Institute for Research and Evaluation reported Community Marriage Policies cut cohabitation rates by a third, and reduce divorce rates by 17.5% in seven years. (Disclosure: my wife and I helped 11,000 churches create 229 Community Marriage Policies and trained Mentor Couples to implement them.)

Michael J. McManus is President of Marriage Savers and a syndicated columnist