“Middle class” has become a meaningless political term covering everyone who is not on food stamps and does not enjoy big capital gains. Like a sociological magician, I can make the middle class grow, shrink or disappear just by the way I choose to define it.
What is clear and incontestable is the growing inequality in this country over the last three decades. In a 180-degree reversal of the pattern in the decades after World War II, the gains of economic growth flow largely to the people at the top.
I like the idea of a sociological magician but this is an important issue: many Americans may claim to be middle class but their life chances, experiences, and tastes can be quite different. Just look at the recent response to possible changes to the 529 college savings programs. A vast group may help political parties make broad appeals yet it doesn’t help in forming policies. (Just to note: those same political parties make bland and broad appeals even as they work harder than ever to microtarget specific groups for donations and votes.)
Given some recent conversations about the relative lack of influence of sociologists, perhaps this is an important area where they can contribute. Class goes much further than income; you would want to think about income, wealth, educational attainment, the neighborhood in which one lives, cultural tastes and consumption patterns, and more. The categories should clearly differentiate groups while remaining flexible enough to account for combinations of factors as well as changes in American society.