I shouldn't have said "most". It's more like 34% of the top 20% fall to a lower quintile over six years according to a Federal Reserve Bank of Minneapolis stud

I shouldn't have said "most". It's more like 34% of the top 20% fall to a lower quintile over six years according to a Federal Reserve Bank of Minneapolis study of households from 1002 to 2007. (http://www.minneapolisfed.org/research/qr/qr3411.pdf http://www.minneapolisfed.org/research/qr/qr3411.pdf) I should have looked this up instead of just trusting my memory. Still pretty significant.