Women think that by living with a man, they are taking a step toward marriage. However, many men cohabit to avoid a commitment to marriage. They like female companionship, available sex and sharing of rent.

However, their clash of values prompts most cohabitators to break up. While two-thirds of those marrying are cohabiting, that's only 1.5 million couples.

What happened to the other 6 million? They broke up, experiencing "premarital divorce" which is as painful as a real divorce. It is particularly devastating for women, who often never marry.

Indeed, there were only 21 million never-married Americans in 1970 but 63 million in 2010. That's a tripling at a time the population grew only 50%.

No wonder America's marriage rate has plunged 54% since 1970.

What's more, cohabiting couples who do marry - are more likely to divorce than those who remained apart until the wedding. Various studies say the odds increase by 26% to 65%.

Thus, cohabitation is a snake which both diverts tens of millions from marrying, and increases the odds of divorce for those who do marry.

Result: three-fourths of adults used to be married. Now only half are.

What has been less recognized is that cohabitation is devastating to children.

Most unwed births are to cohabiting couples. Out-of-wedlock births have jumped from 5% of births in 1960 to 41%, paralleling soaring cohabitation.

That figure is 20 times the 2% out-of-wedlock birth rate in Japan.

"Cohabitation has replaced divorce as the main reason for family instability today. By age 12, about 24% of children will have experienced the divorce of their married parents, versus 42 percent of children who will live with cohabiting parents," according to "Why Marriage Matters," writes Alysse ElHage in "Family North Carolina."

These children are more likely to have behavioral and health problems, and to fail in school, and are six times more likely to be poor than those with married parents.

Brad Wilcox, director of the National Marriage Project, describes their plight as "the dark underbelly of cohabitation. Children in cohabiting households are significantly more likely to suffer from physical, emotional and sexual abuse than children in either intact married families or single parent families." A question: have you ever heard a sermon opposing cohabitation? I bet not. I have asked hundreds of pastors in different cities if they have ever preached on it, and only one hand in 50 goes up.

Why? Paul wrote to the Corinthians, "Flee fornication." What is cohabitation but fornication raised to the 100th power? What could your pastor say, after quoting Scripture? "You can't practice permanence." Evidence: nine out of ten couples who begin their union cohabiting - will break up before or after the wedding. "There is a better way to test the relationship" with a premarital inventory and by meeting with a Mentor Couple to discuss the issues that it surfaces.

My wife and I pioneered training couples in healthy marriages to be Marriage Mentors in our home church in the 1990s. During that decade, our Mentor Couples prepared 288 couples for marriage, 58 of whom decided not to marry. That's a huge 20% who discovered they had chosen the wrong person. Of the 230 couples who did marry, we know of only 16 divorces. That's a 7% failure rate - or a success rate of 93% over two decades. That's virtual marriage insurance.

Another reason for soaring cohabitation is government pays for it. If a woman has a unwed birth, she is not asked if she is living with the father with access to his income as if married. Government thinks of her as a single mom needing welfare, Medicaid, food stamps, and subsidies costing taxpayers $20,000 a year in 2004 according to Heritage Foundation. However, if she marries the father, (in the best interest of all) she loses virtually all subsidies.

Result: unwed births rise and marriages plunge each year. I suggest that a Presidential candidate or a governor might say, "I propose that if any cohabiting couple with a child decides to marry, government will not reduce benefits for two years, and after that, they would be tapered off over 3-4 years." That would save billions by reducing cohabitation and increasing marriage, protecting children .

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