I doubt that you will **ever** show that the physical size of the American middle class has shrunk with any rational look at available demographic data.
Consider that to be a challenge.
Ah, Southack, it's not just that you're in the middle class, it's WHERE you are in the middle class. If the middle class is considered to be, say, between $30,000 and $100,000 per year for a family of four, someone can go from making $90,000 a year to $35,000 a year but not show up on the resolution of the radar screen you're looking at. But I can guarantee that THEY'LL perceive the difference quite clearly.