The shift to tougher penal policies three decades ago was credited with helping people in poor neighborhoods by reducing crime. Now that the U.S. incarceration rate has risen to the world's highest, social scientists find the social benefits to be far outweighed by the costs to those communities. “Prison has become the new poverty trap,” said Bruce Western, a Harvard sociologist. “It has become a routine event for poor African-American men and their families, creating an enduring disadvantage at the very bottom of American society.” Among African-Americans who have grown up during the era of mass incarceration, one in four has had a parent locked up at some point during childhood. Some families benefit after an abusive parent or spouse is locked up. Still, Christopher Wildeman, a Yale sociologist, found that children are more likely to suffer academically and socially after the incarceration of a parent. Boys left fatherless become more physically aggressive. Spouses of prisoners become more prone to depression and other mental and physical problems. Before the era of mass incarceration, there was evidence linking problems in poor neighborhoods to the high number of single-parent households and also to the continual turnover on many blocks as transients moved in and out. Now those trends have been amplified by the prison boom's “coercive mobility,” says Todd Clear, dean of the School of Criminal Justice at Rutgers University. In some low-income neighborhoods, he notes, virtually everyone has at least one relative currently or recently behind bars, so families and communities are continually disrupted by people going in and out of prison.