I often distinguish between the "fortunate fifth" at the top of the social structure, and everyone else.
My friend David Blankenhorn argues that the real divide in America is not between the 1% and the 99%, nor between the federal government and everyone else - the favorite division points of the left and the right, respectively. Instead, he says the real divide is between the top 30% and everyone else.
The top group is likely to have a college education, stable jobs, stable marriages, and avoid self-destructive habits.
Statistically, one could argue well for either cut point. The central issue is that a sizable minority are doing well, while those below live with increasing uncertainty.
From now on I will talk about the Thriving Third. This is supportable empirically, and has the advantage of being more hopeful to those in the middle.