Definitions for this are all over the place. Fussell's "upper middle class" lifestyle couldn't be stably maintained by households under the top quintile (probab

Definitions for this are all over the place. Fussell's "upper middle class" lifestyle couldn't be stably maintained by households under the top quintile (probably not under the top 10%, even), nor could the upper-middle (also upper, but largely upper-middle) described in the jokey-but-fairly-accurate Official Preppy Handbook, and those books are ~40 years old now. For one thing, both paint decent-or-better private prep school as key for that class, and that's never really been within the reach of the lower four quintiles, to say nothing of the other things you'll need to spend money on to stay in that class.