Paul Krugman explains.
Larry Mishel has a systematic breakdown of the reasons for worker income stagnation since 1973. He starts with the familiar divergence: productivity up 80 percent, the compensation (including benefits) of the median worker up only 11 percent. Where did the productivity go?
The answer is, it’s two-thirds the inequality, stupid. One third of the difference is due to a technical issue involving price indexes. The rest, however, reflects a shift of income from labor to capital and, within that, a shift of labor income to the top and away from the middle.
What this says is that widening inequality makes a huge difference. Income stagnation does not reflect overall economic stagnation; the incomes of typical workers would be 30 or 40 percent higher than they are if inequality hadn’t soared.