http://faculty.chicagogsb.edu/christian.broda/website/research/unrestricted/Broda_TradeInequality.pdf

...for the full article.

http://lanekenworthy.net/2008/05/20/inequality-and-prices/

...for a synopsis.

It analyzes the 'increasing wealth disparity' in the US, and takes a more in-depth look than most news organizations would.