A strong middle class
This is one of the biggest stories of our time: the middle class… especially the lower middle class… is being decimated.
A strong middle class has long been the hallmark of modern western civilization.
In fact, history shows that throughout many dominant empires, from ancient Rome to the British Empire, a robust middle class is essential to maintain a durable society.
Where the middle class is strong and growing, civilization flourishes.
And where the middle class fails, civilization turns over.
Don't know if this as true, but it seems logical that it would be the case: When the middle class disappears, the rich will have to spend more and more money protecting themselves, and eventually the people aren't going to stand for it anymore, and they'll revolt.