When Americans used to brag about “the American way of life”—a phrase still in common use in 1960—they were talking about a civic culture that swept an extremely large proportion of Americans of all classes into its embrace. It was a culture encompassing shared experiences of daily life and shared assumptions about central American values involving marriage, honesty, hard work and religiosity.

Over the past 50 years, that common civic culture has unraveled. We have developed a new upper class with advanced educations, often obtained at elite schools, sharing tastes and preferences that set them apart from mainstream America. At the same time, we have developed a new lower class, characterized not by poverty but by withdrawal from America’s core cultural institutions…

If you were an executive living in Belmont in 1960, income inequality would have separated you from the construction worker in Fishtown, but remarkably little cultural inequality. You lived a more expensive life, but not a much different life. Your kitchen was bigger, but you didn’t use it to prepare yogurt and muesli for breakfast. Your television screen was bigger, but you and the construction worker watched a lot of the same shows (you didn’t have much choice). Your house might have had a den that the construction worker’s lacked, but it had no StairMaster or lap pool, nor any gadget to monitor your percentage of body fat. You both drank Bud, Miller, Schlitz or Pabst, and the phrase “boutique beer” never crossed your lips. You probably both smoked. If you didn’t, you did not glare contemptuously at people who did…

As I’ve argued in much of my previous work, I think that the reforms of the 1960s jump-started the deterioration. Changes in social policy during the 1960s made it economically more feasible to have a child without having a husband if you were a woman or to get along without a job if you were a man; safer to commit crimes without suffering consequences; and easier to let the government deal with problems in your community that you and your neighbors formerly had to take care of.

But, for practical purposes, understanding why the new lower class got started isn’t especially important. Once the deterioration was under way, a self-reinforcing loop took hold as traditionally powerful social norms broke down.