The half-century between 1912 and 1962 was a period of great wars and economic tumult but also of impressive social cohesion. Marriage rates were high. Community groups connected people across class.

In the half-century between 1962 and the present, America has become more prosperous, peaceful and fair, but the social fabric has deteriorated. Social trust has plummeted. Society has segmented. The share of Americans born out of wedlock is now at 40 percent and rising.

As early as the 1970s, three large theories had emerged to explain the weakening of the social fabric. Liberals congregated around an economically determinist theory. The loss of good working-class jobs undermined communities and led to the social deterioration.

Libertarians congregated around a government-centric theory. Great Society programs enabled people to avoid work and gave young women an incentive to have children without marrying.