Interestingly, Americans have more belief that their society is a meritocracy than most developed nations and so are especially unaware of the problem. I submit it is this commonly held perception rather than data that is informing you comment.
Obviously in the past, when democracies were even fewer in number, the situation may have been different.
Here[1] you'll find a bounty of links supporting my point were one to take time time to read it rather than instantly and silently down voting what one doesnt want to know.
[1]https://en.wikipedia.org/wiki/Social_mobility#Patterns_of_mo...