The last three are by far the most important, and they are interrelated. The poor are the ones who can't afford family planning. They are the most likely to be abused, which can lead to a lifetime of self-loathing and promiscuity. Kids who have grown up poor are likely to have kids very young, to have many of them, and to raise them in poverty, continuing the cycle into the next generation. Durning and Crowther make this argument in words and anecdotes, but most strikingly, they make it in statistics.
Absent dads are ten times as likely to be current on their car payments as on their child support.
Colleges graduates in the U.S. typically have 1.6 to 2.0 children. High school graduates average 2.7 children. High school dropouts average 3.2 children. Children from poor families are 18 times more likely to be sexually abused as children from middle-class families. The assault is 200 times more likely to come from someone in the home than from a stranger.