Inequality Is Up a Lot. The Question Is: How Much?

Inequality in the U.S. has risen a lot during the past few decades. This has sparked outrage among segments of the public, raised concern among economists and other social scientists, and revitalized America's socialist movement.

Much of the debate has been driven by the work of three French economists -- Thomas Piketty, Emmanuel Saez and Gabriel Zucman. The trio has put out a huge amount of impressive work, digging into historical archives and patching together a diverse array of modern data sources to graphically depict how income and wealth have become more concentrated. They have also helped design some of the bolder Democratic tax plans.