From Larry Summers’ review of Piketty:

When Forbes compared its list of the wealthiest Americans in
1982 and 2012, it found that less than one tenth of the 1982 list was
still on the list in 2012, despite the fact that a significant majority
of members of the 1982 list would have qualified for the 2012 list if
they had accumulated wealth at a real rate of even 4 percent a year.
They did not, given pressures to spend, donate, or misinvest their
wealth. In a similar vein, the data also indicate, contra Piketty, that
the share of the Forbes 400 who inherited their wealth is in sharp decline.

HT: David Levey