From the New York Times’s Economix:
Only half of Americans are wealthier than their parents were. What’s more, children born into the top wealth quintile were least likely to surpass their parents’ affluence…Nearly three-quarters of people born into the bottom of the wealth distribution ended up richer than their parents were, whereas only one-quarter of people born into the very top of the wealth distribution accumulated a bigger fortune than their parents had.
Don’t get too excited for the poor:
If you grew up with parents who were broke, for example, having even a dollar to your name technically makes you richer than your folks. But you still don’t have any semblance of financial security.
Furthermore, breaking out of the income class you were born into is pretty difficult:
Of Americans born into the bottom quintile of wealth, 41 percent remain there in adulthood