It is the primary liberal argument that America’s primary economic problem is growing income inequality.

For three decades, in this view, the rich have grown richer while middle-class incomes have stagnated. This emphasis on economic discontents is purposeful. Any political coalition for income redistribution that does not include middle-income voters will fail. So the message has been: Suburbanites of the world, unite. You have nothing to lose but your student loans.

There remains a considerable amount of economic mobility, upward and downward, in the middle class. But nearer the bottom of the income scale, upward mobility is weak and stuck. As a result, according to the Economic Mobility Project, the U.S. economy is less fluid than the economies of Canada, France, Germany or the Scandinavian countries. 

Read the full article at washingtonpost.com.