The difference between the median and the average strikes again! The popular comparison is that median real wages have only risen slightly from the 70s while average productivity (because by definition the labor productivity numbers are averages) has risen substantially. But much of that is due to the increases in productivity from high productivity individuals, say maybe those whose job it is to tell fancy electronic machines how to do low skill repetitive tasks. Some of those people might even browse this forum!

There is actually fairly weak data to support the popular theory of a decreasing labor share of income (and thus an increasing capital share) causing more inequality and to the extent such an effect could exist its size is only a few percent of GDP over the past few decades.