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Krugman's response? That Ferguson's response is pathetic.
Here's what Krugman emails to Business Insider:
What a pathetic response. Notice that he is doing precisely what I never do, and making it about the person as opposed to his ideas. All I have ever done to him is point out that he seems to not know what he is talking about, and that he has been repeatedly wrong. I would never stoop to speculating about his childhood! If he can't handle professional criticism -- which is all that I have ever offered -- he should go find another profession.