No doubt that the middle class is under pressure, but...
I suspect that if your read through the data, you will see that this study is focused on what were formerly big city middle class neighborhoods, going back to 1970.
This is less about income inequality than it is about the decline of industrial cities and a migration of their working populations away and out to the ‘burbs. It is a function of the changes in the economy away from heavy manufacturing toward a service and information-based economy.
No, it's not under pressure, it's being decimated.