[nickik]

Usually mobility doesn't happen in one generation but like 2-3. A poor person managed to get middle class or upper middle class and their children then are in prime position to make another jump.

If you just look at the Top 20% you can see how people drop into and out of it over generations.

So, garbage man to millionaire, is pretty rare if your grand father was a garbage man from Korea in the 70s your life now is probably comparable to most people from the US.