Last month I read an article that first appeared in the Huffington Post titled "X Marks the Spot Where Inequality Took Root: Dig Here".
It explains how real wages in the US shadowed growth in productivity in the years after World War II. But in the mid-1970s wages growth completely stalled.
If wages had continued to shadow productivity growth they would now be double what they are today. This explains a lot about contemporary US society: all the gains of increased productivity have been absorbed by the rich.