UPDATE: Krugman sez: What we're seeing isn't the rise of a fairly broad class of knowledge workers. Instead, we're seeing the rise of a narrow oligarchy: income and wealth are becoming increasingly concentrated in the hands of a small, privileged elite.
...Highly educated workers have done better than those with less education, but a college degree has hardly been a ticket to big income gains. The 2006 Economic Report of the President tells us that the real earnings of college graduates actually fell more than 5 percent between 2000 and 2004. Over the longer stretch from 1975 to 2004 the average earnings of college graduates rose, but by less than 1 percent per year.
So who are the winners from rising inequality? It's not the top 20 percent, or even the top 10 percent. The big gains have gone to a much smaller, much richer group than that.
A new research paper by Ian Dew-Becker and Robert Gordon of Northwestern University, "Where Did the Productivity Growth Go?," (PDF) gives the details.