Chart plotting union density against inequality. When union density is low, inequality is higher.
As the chart above from Unions Work shows, over the past nearly hundred years of American history, when union density has been low, inequality has been high. Union density isn't theonly factor in that, of course. But it's not a coincidence. Neither is this:
Chart showing that union density and middle class share of the national income have declined along similar lines.
There are lots of complicated economic and political factors. But they tend to boil down to upward shifts in money and power, and workers getting squeezed. Even if you're not in a union, the fate of unions affects us all.