THE DEFENSE OF MARRIAGE IS THE WAR ON INEQUALITY:

Putnam moves seamlessly from these stories to social-science data that confirm a truth understood by specialists for some years now. Beginning with the publication of Daniel Patrick Moynihan's 1965 report The Negro Family, a broad consensus formed that poverty among African-Americans and the attendant ills of drug use and crime were directly connected to the decline of two-parent families. It turns out, however, that African-Americans were the canary in the coal mine, and that the social decline that hit residents of inner cities in the 1970s and 1980s has now spread to the entire white working class.

Putnam defines social class by education: with technological advance, the premium on higher education has risen relentlessly. For Americans with a bachelors degree or higher, the past three decades have seen both rising incomes and a huge restoration of family values, while, for their less educated peers, this period has been an utter disaster. One of the most sobering graphs in Our Kids shows that while the proportion of young children from college-educated backgrounds living in single-parent families has declined to well under 10 per cent, the number has risen steadily for the working class and now stands at close to 70 per cent. This is the same percentage that rang loud alarm bells when it happened to the black community a generation ago.

Putnam then goes on to explain, through the lens of accumulated social-science research, how important parenting and family structure are to life outcomes for children. Early childhood stimulation, appropriate role models, stable expectations and family dinners are all part of the environment needed to produce upwardly mobile adults, and almost all are lacking today for Americans from less educated backgrounds. Many people overcome dysfunctional families, but it is far easier to do so with adequate resources. Economic inequality thus becomes self-reinforcing through the mechanism of absent families.

Putnam points out that while both gender and racial equality have greatly improved over this period, the gains have been completely offset by widening class differences. College-educated Americans have been pulling away from their high school-educated peers within subgroups such as African-Americans, Hispanics and women. There is today a substantial upwardly-mobile black middle class that, like its white counterpart, has moved to the suburbs and segregated itself from the poor.

Back in the 1980s, the debate over black poverty was polarised between liberals who blamed structural (ie economic) factors such as the decline in manufacturing jobs, and conservatives who denounced permissiveness and shifting cultural norms for the breakdown of families. Putnam makes very clear that both of these causes are at work in the present crisis. The huge erosion of middle-class jobs in countless manufacturing industries has led to a decline in real incomes of 22 per cent since 1980 for high-school dropouts, and 11 per cent for high-school graduates. But culture also matters: while rising joblessness produces social dysfunction in all societies, the stresses of the Great Depression did not lead to an explosion of single-parent families because of cultural norms then in place, such as the stigmatisation of unwed parenthood and shotgun weddings. Conservatives who see family breakdown as a simple matter of cultural decay, however, have to explain the emergence of "helicopter parents" and steadily strengthening family bonds among the college-educated.

The data in Our Kids parallel many of the findings in Charles Murray's 2012 book Coming Apart: The State of White America 1960-2010. Putnam, however, does not have Murray's libertarian blinders and recognises that government policies such as the Morrill Act of 1862 and the 1944 GI Bill were critical in reducing inequality in earlier periods of American history. The final chapter of Our Kids focuses on policy solutions, and runs through a familiar list of interventions, including expansion of the earned income tax credit, increasing use of long-term contraceptives, reducing sentencing for non-violent crimes (which keeps many poor fathers away from their children), a renewed focus on vocational education, better mentoring and extracurricular activities, and outright cash transfers to the poor.

Follow @brothersjudd