[zozbot234]

> What about bottom incomes? Why have those barely increased in real terms in the last 30 years

Because the main source of productivity growth in that period was technical change, and those who were not well positioned to adapt were stuck at the bottom of the income ladder. Of course there were other factors (globalization, increasing costs in some sectors putting pressure on real incomes etc.), but that's the main story. It's quite consistent with Graham's argument.