What's the best thing parents can do to ensure their children's future prosperity? Stay married.

No, you haven't wandered into the middle of a sermon, and this isn't just my opinion. The latest social science research shows children from divorced homes are far more likely than children from married homes to live in poverty. They are also less likely to earn a decent income themselves when they become adults.

In fact, the marital status of a child's parents largely determines whether that child lives above or below the poverty line, according to my colleague Patrick Fagan, a cultural expert and former family counselor. "Poverty is the result of many factors," he writes in a recent report, "but most have to do with marriage, sex before marriage, living together outside of marriage, and divorce after marriage."

Among his findings:

• Divorce reduces the income of families with children by an average of 42 percent. Almost 50 percent of these families live in poverty.

• Nearly 75 percent of families in the bottom fifth of income have only one parent, while 95 percent of families in the highest fifth are headed by married couples.

• Three-quarters of all women applying for welfare do so either because of a divorce or because a live-in relationship has ended. The ones who leave the welfare system when they get married are the least likely to return.

• Married couples in their mid-50s amass four times the wealth of divorced individuals (an average of $132,000 versus $33,600).

The harmful effects of divorce go beyond lost income. The children of divorced parents are more likely to have out-of-wedlock children and twice as likely to "shack up," as they used to say, than are the children of married parents. They are also twice as likely to drop out of high school and 25 percent to 50 percent more likely to develop behavioral problems such as anxiety, depression and hyperactivity.

And contrary to popular belief, so-called "trial marriages" (a euphemism for shacking up) actually lead to more divorces-and hence more poverty. Couples who live together before marriage are twice as likely to end a marriage. The divorce rate quadruples for those who have lived together with someone other than a future spouse.

Uncovering the link between poverty and divorce raises a question: What can we do about it? We've seen the results of Washington's so-called war on poverty: a "great society" wracked by welfare dependency and single-parent homes. If lawmakers really want to help poor children, they should promote policies that support marriage, such as changing the Earned Income Tax Credit so women who wed the fathers of their children don't lose their benefits. Perversely enough, the current law actually gives poor women a reason not to get married.

State governments can help by enforcing child-support laws and making divorces harder to obtain when children are involved. But local efforts can have the largest impact. For example, church leaders and non-profit organizations can prepare couples for marriage by fostering local "community marriage covenants." Such groups should also encourage regular religious worship by families-which research shows reduces the risk of divorce.

The stakes are high. "The effects of marital breakdown on national prosperity and the well-being of individual children are like the action of termites on the beams in a home's foundations," Fagan says. "They are weakening, quietly but seriously, the structural underpinnings of society."

Edwin Feulner is president of The Heritage Foundation (www.heritage.org), a Washington-based public policy research institute.