I think you're on the right track here. To me, the middle class is defined not by assets, but by having your survival and security reasonably assured -- to the

I think you're on the right track here. To me, the middle class is defined not by assets, but by having your survival and security reasonably assured -- to the point, as you say, that you don't have to spend all your time worrying about them. You have to work, but you have some free time and disposable income.