According to a recent paper posted by Emmanuel Saez and Gabriel Zucman, "the rise of wealth inequality [in the U.S. in recent decades] is almost entirely due to the rise of the top 0.1% wealth share, from 7% in 1979 to 22% in 2012."
Saez presented this paper yesterday (Wednesday) at the University of British Columbia in Vancouver. I was actually in Vancouver at the start of the day, by reason of my having presented my Piketty paper (coauthored with Joe Bankman) on Monday, but a change to my flight time prevented me from attending the session.
Here are the slides for my talk from my prior presentation of the paper at Virginia - all that changed in the interim was the title page. And the photo here was taken right after the talk - I am only actually, not figuratively, backed up against a fence.