Criminologists have long suspected the absence of a father in the home is an important factor in leading boys into violence and crime. But since there are so many other variables involved -- such as a the mother's education, race, income, unemployment rates and even cognitive ability -- it has been impossible to say with any certainty how family structure alone figures in the equation.

Now, Cynthia Harper of the University of California and Sara McLanahan of Princeton University have utilized a large national database, the National Longitudinal Survey of Youth, to control for those variables and isolate the family structure question. Among their findings:

• Boys raised outside of intact marriages are, on average, more than twice as likely as other boys to wind up in jail -- with each year spent without a dad increasing the odds of future incarceration by 5 percent.

• A child born to an unwed mother is about 2.5 times more likely to end up in prison, while one whose parents split during his teen years was about 1.5 times more likely to be imprisoned.

• Boys living in step-parent families were almost 3 times as likely to face incarceration.

• While living in poverty made it more likely a boy would go to jail, family structure was more important than income.

Teenage boys living with just their single fathers were no more likely to commit crimes than boys coming from intact families. But boys living with remarried fathers faced rates of future incarceration as high as or higher than boys living with remarried mothers.

Source: Maggie Gallagher (Institute for American Values), "Fatherless Boys Grow Up Into Dangerous Men," Wall Street Journal, December 1, 1998.