Not enough divisions...I mean, it can be helpful to try to put things into broad categories, but, ya, that definition of 'upper class' is too low here, even for just three broad income levels.
Another point: I would expect these findings to be muddied by the differences in cost of living between areas. $300 a month rent in city A compared to $1200 a month rent in city B for pretty much the same apartment in the same kind of area of town, etc.
Try it by educational level attained. For instance, what percentage of the population (male, female, both) has only a high school education and no college? What is their medium income? How do the population numbers, education and income compare with the category which possesses a professional degree?
Pretty quick you start to see that $86,000 is most definitely outside the middle class.
It is a elusive thing. Middle class once meant pretty much business ownership and a particular set of values. Upper class generally meant that one did not work, though someone in the family might manage the family's business, and a whole other set of values.
Now it seems to be mostly income level, and one could be a middle manager in a large business. Values are almost uniform across "classes." Now a days one can go across a broad spectrum of income in a lifetime as well, but inflation is also quite wild too or one's life.
The probably need to just group them as "income brackets," but of course they would have to give up their marxists terminology.
If they are just figuring this out now, then they are dumber than I thought.
BTW, there is no thrid way, if you ask me. The democrats need to junk the whole socilist business. After all the Democrat party is older than the legacy of FDR. Fat Chance though.