Some academics and advocates, including Cohen here, counter that mass incarceration is actually creating more single-parent families. That argument rests on the questionable assumption that men who are in prison would become reliable presences in their children's lives if freed. Worse, it implies that children—or their mothers—would be better off with a violent father in the house than on their own. There are valid concerns about our harsh drug policies, but the truth is the percentage of prisoners behind bars for drugs is relatively modest. According to the BJS, about 20 percent of the current state prison population has been convicted of drug offenses while 50 percent are doing time for violent crimes. (Federal percentages, though not the number of actual prisoners, are higher.) Violent offenders accounted for 60 percent of the rise in the state prison population between 2000 and 2008, a time when the percentage of drug offenders declined.

It would be easy to make nifty charts showing a strong correlation between the increase in the number of police in D.C. and the rise of single-parent homes or one highlighting the striking parallel in the growth in the nation's prison population and the soaring numbers of nonmarital births. But without careful regression analysis—controlling for other possible reasons for a rise in police and prison numbers—the charts would be, at best, suggestive. So it is with the inverse correlation between family breakdown and crime rates shown in Cohen's charts.

Moreover, the charts ignore social science truism that correlations existing on the individual level—i.e. children of single mothers and criminal actions—do not necessarily translate to the aggregate, i.e. children of single mothers and official crime rates. Consider this other example: Crime did not increase during the Great Recession; in fact, violent crime in the United States fell to a 40-year low in 2010 even while poverty was on the rise. Yet we know that poor are more likely than others to commit crimes. We could design a chart demonstrating that crime rates and poverty rates are unrelated and ask for an apology from the many pundits who have insisted they had to be, but those pundits would rightly object that on its own, the chart can't prove that poverty doesn't cause crime.

The bottom line is that there is a large body of literature showing that children of single mothers are more likely to commit crimes than children who grow up with their married parents. This is true not just in the United States, but wherever the issue has been researched. Few experts, including Cohen, dispute this. Studies cannot prove conclusively that fatherlessness—or any other factor—actually causes people to commit crimes. For that, you'd have to do the impossible: take a large group of infants and raise each of them simultaneously in two precisely equivalent households—except one would be headed by a father and mother and the other by a lone mother. But by comparing criminals of the same race, education, income, and mother's education whose primary observable difference is family structure, social scientists have come as close as they can to making the causal case with the methodological tools available.

To say this is not to "scapegoat" or "blame" women; for one thing, fathers also play a role in the making of single-mother families. For another, blame personalizes what is a huge, global, and multi-causal demographic shift; it's like saying economists are blaming laid-off employees for noting the decline in manufacturing jobs. But it is to caution that the societal consequences of that shift can't be wished away by a simple graph.

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