Prisoners sleep on the floor in the Marion County Lockup in Indianapolis, Indiana.

© 2001 AP Photo

The US criminal justice system may be on the verge of its biggest overhaul in decades. Senator Jim Webb (D-VA) is sponsoring a bill to establish a blue-ribbon commission to conduct a comprehensive review of the criminal justice system and make recommendations for reform. Legislation has been introduced to eliminate mandatory minimum sentences, reduce penalties for some drug offenses, and make other significant changes. As lawmakers consider these reforms, they should remember not only those who are sent to prison, but also the children they leave behind.

The United States incarcerates more people than any other country on earth, with almost 2.4 million persons behind bars on any given day. That figure, though, actually understates the number of people being locked up; the Bureau of Justice Statistics (BJS), a division of the US Department of Justice, estimates that more than 13 million people pass through the nation's jails in a single year.

Of course being the world's leading prison nation comes with a price tag. The average annual operating cost for a prison bed -- the amount it costs to incarcerate one person for one year -- is about $24,000; in some states, it's more than $40,000. All told, the United States spends about $60 billion a year on locking people up.

But there are also other, less obvious costs, including the effects on children left behind when parents are sent away to prison. Christopher Wildeman, a University of Michigan sociologist who has studied the issue, concludes in a recent article that "parental imprisonment has emerged as a novel-and distinctively American-form of childhood disadvantage."

How extensive is the problem? A 2008 BJS study estimated that more than 1.7 million children under 18 had a parent in prison as of mid-2007. That's a one-time snapshot; the number of children who have a parent incarcerated at some point during their childhood is much higher. And as the US prison population has surged, so has the number of children with an incarcerated parent, nearly doubling between 1991 and 2007.

Like every other aspect of the US criminal justice system, parental incarceration falls with crushing disproportionality on African Americans. The BJS study found that as of mid-2007, a black child was about eight times as likely as a white child to have a parent in prison.

Dr. Wildeman estimates that while the fathers of one in 25 white children born in 1990 had been in prison by the time the child turned 14, for black children born in the same year, the figure was one in four. For black children whose parents didn't finish high school, the figure was more than one in two. Perhaps most ominous, Dr. Wildeman found that racial inequality in rates of parental incarceration is increasing over time.

In a 2002 report, Human Rights Watch documented the harmful effects on children whose parents had been sent to prison for drug offenses in New York state, concluding that children had become "collateral casualties" in the so-called "war on drugs." Some of these effects are obvious and immediate. If the incarcerated parent was a wage-earner, the loss of income hurts the family economically, in some cases leading to poverty or homelessness. If the parent was the sole caretaker of young children, the parent's incarceration may require their placement in foster care. Although there may be rare cases-a physically or sexually abusive parent, for example-in which removing the parent from the home benefits children, for most the loss of a parent to incarceration is a traumatic and devastating event.

There are other, longer-term consequences as well. There is evidence that children of incarcerated parents are at increased risk for a range of emotional and behavioral problems, including post traumatic stress disorder, problems at school, delinquency, and aggression. One study found that children of incarcerated parents are six times as likely as their peers to end up in prison themselves.

It's long been fashionable for politicians to boast that they're "tough on crime." But by getting tough on crime, the United States has also gotten tough on children. As we take a long-overdue second look at the policies that have given us the world's highest incarceration rate, let's not forget prison's littlest victims.