The Rise of the Middle Class

I just found out today from The Lexus and The Olive Tree that the large middle class is a mid-twentieth century phenomenon (I thought it has always been the case). It is a recent phenomenon that never occurred before in history.

I find this interesting because it opens a lot of questions. Does that mean that the gap between the rich and the poor (because there was no middle class in between) was extremely wide before mid-twentieth century? What caused this rise of large middle class?
And what was it like to live in a society without a large middle class? (It seems we will be living in such a society in several decades or even sooner.)

One large topic to research on :)

(Edited on 5 March 2015)


(Added on 5 March 2015)
I recommend reading The Lexus and the Olive Tree by Thomas Friedman. It gives a broad overview of history that leads up to globalization that we are experiencing today.

Friedman followed this up with another book, The World is Flat ("flat" in the sense that opportunities are more fairly available, as in "a flat playing field"). I also recommend reading this.