Who said this? Paul Samuelson. Yes, that Paul Samuelson, the Nobel Prize winner who wrote the intro economics textbook we all studied, and longtime booster of free trade and globalization. I found it in this worthy American Prospect article, Offshoring Silicon Valley, and tracked it down to this New York Times interview. And here's the link to the 4-year-old Samuelson article (subscription required) which says this in the abstract:
[T]he winds of dynamic comparative advantage cannot be counted on to create in each region new net gains of the gainers assuredly greater than the new net losses of the losers.
So now that Dr. S. has confirmed that it is theoretically possible for us to see what we've been seeing, it's finally OK to believe our own lying eyes.
Now look who else is saying substantially the same thing--Robert Rubin, the Clinton Administration's greatest booster of globalization.
Months ago, Mr. Rubin had said that while he favored Mrs. Clinton as the better candidate, he could easily support Mr. Obama, if he won in the long primary process. He said, for example, that a passage on the impact of globalization in Mr. Obama's book "The Audacity of Hope" came out of a conversation the two men had. "Without question, the pressure on wages and incomes have [sic] become greater and we need to focus on those issues," Mr. Rubin said, citing himself as a source for that point.
This NBER report on the Impact of Trade and Offshoring on American Workers reaches the same conclusion.