@pettter Well, there are several ways:
1. Assets and Income, i.e. "I am upper-middle class, because my income exceeds median + 20% and my assets exceed median
2. Distribution of time between labor necessary to survive vs in self-directed activities (i.e. I do income-generating work 20 hour week, speculative work 8 hours a week, and pro-bono work 4 hours per week)