Alarming statistics. Unmarried cohabitation—the status of couples who are sexual partners, not married to each other, and sharing a household—has increased by 1,200 percent or more than tenfold between 1960 and 2005.

Estimates indicate that about a quarter of unmarried women age 25 to 39 are currently living with a partner. An additional quarter have lived with a partner at some time in the past. Over half of all first marriages are now preceded by living together. A growing percentage of cohabiting couple households, now over 40 percent, contain children.

Who cohabits? Studies show it is generally the poor and less educated, less religious, divorced or those growing up in a home where there has been parental divorce, no father present in the home, or high levels of marital discord.

The cohabiters are less likely to say that premarital sex is wrong, less inclined than non-cohabiting married parents to see unmarried childbearing as bad for society or morally wrong and are less inclined to say a child needs both a mother and father to grow up happily. To me, these are convenient rationalizations for poor choices they have made.

Cohabitation: not a trial marriage. Cohabitation and marriage share some things in common - shared physical space, emotional and sexual intimacy, and a division of assets and labor. Cohabitation, however, is a vague and more transitory arrangement.

People who live together or have cohabited in the past reject the notion that cohabitation is a testing ground or a stepping stone to marriage by a 2:1 margin. They cite ease or desire to live together, finances or specific concerns about marriage. The lack of commitment to a durable relationship figures prominently in their thinking. Only 8 percent explicitly intend their living together arrangement as a stepping stone to marriage.

About half of all cohabiting relationships in this country end within five years. If a cohabiting relationship does last for five years, there is a ninety percent probability that it will eventually lead to a marriage.

Cohabiters who eventually marry have a higher divorce rate than those who do not live together before marriage. If a long lasting, loving marriage is the goal, then living together before marriage prepares them more for failure than success.

Why the higher divorce rate among cohabiters who eventually marry? Researchers have two theories that are intertwined: the "selection effect"and the "experience of cohabitation effect." The "selection effect" refers to the fact that people who cohabit before marriage have different characteristics from those who do not. The willingness to engage in high risk and unconventional behavior such as cohabitation also leads to marital instability.

The "experience with cohabitation" effect means that the couple learns and practices poor relationship

habits during cohabitation (avoidance of conflict and/or poor conflict resolution skills, lack of unity with money management, and more selfish, self-serving behavior) due to the low commitment levels.

There is data supporting both theories.

However, one bright note. Relationships that limit premarital sex and cohabitation to their future spouse do not have higher divorce rates and marital discord. If a couple enters a cohabiting relationship with a date certain of their marriage, then the likelihood of divorce is not increased.

This constitutes a small percentage of the cohabiters and is a form of engagement based on genuine commitment. Despite that hopeful statistic, there is no evidence that those who cohabit before marriage have stronger marriages than those who do not. For all the rest, cohabitation is trouble and a blind alley for martial happiness.

Broken hearts, mental health issues, domestic violence and child abuse. About two-thirds (68 percent) of those cohabiting think they will marry their current partner someday. The reality is that 50 percent of cohabiting couples don’t make it to the altar. Like a divorce, these couples experience pain, sense of loss, severe anger and damage to self-esteem, but enjoy none of the legal protections. People who cohabit have a higher risk of suicide, depression, chronic and acute illnesses, accidents and lower productivity.

Among cohabiting couples with no plans to marry, 17 percent report partner abuse. Among cohabiting couples with plans to marry, 14 percent report partner abuse. Only five percent of married couples report partner abuse.

The most dangerous place for a child is in a household where the mom is cohabiting with a man who isn’t biologically related to the children. Children are almost 20 times more likely to suffer physical or sexual abuse in these households.

Cohabitation discourages marriage. People who have never married and are not currently cohabiting are optimistic about marriage. Fifty-six percent among this group report wanting to marry, 29 percent are not sure if they want to marry and 12 percent say they don’t want to marry.

When cohabiters were asked whether or not they want to marry, apart from any expectations for marriage with their current partner, those cohabiting are almost evenly divided between expressing a desire to marry and expressing uncertainty about marriage.

By providing an alternative to marriage, cohabitation for some appears to diminish rather than strengthen the impulse to marry and make marriage weaker instead of stronger. Children suffer. Talk about an inconvenient truth. Al Gore and Michael Moore, document this one.

These statistics were gathered from, "The State of Our Unions 2007," published by the National Marriage Project at Rutgers University and from the Pew Research Center survey, "Generation Gap in Values and Behaviors," July 1, 2007.