If a country has a Gini coefficient of zero, its residents are completely equal economically. As the coefficient approaches 1, this indicates increasing inequality.
This matters because, according to a review (by Nicholas Kristof) of Thomas Piketty's "Capital in the Twenty-First Century," the U.S. "now has a Gini coefficient ... approaching some traditionally poor and dysfunctional Latin countries."
Great. In addition, Kristof notes, "equal opportunity is now a mirage. Indeed, researchers find that there is less economic mobility in America than in class-conscious Europe."
Madame L will be reading the Picketty book when it becomes available at her local library, where she has placed a hold on it.... Even though it's 685 pages long. Or maybe Madame L will read a few more summaries and reviews like that written by Kristof.