Even worse than his many errors, is his hypocrisy. He very loudly accused Amazon of being a "monopsony" during Amazon's most recent dust-up with the big publishers, on grounds that its market power would enable it to hurt consumers, although he acknowledged, Amazon hadn't used its economic power that way. https://www.nytimes.com/2014/10/20/opinion/paul-krugman-amaz...
The impetus for Krugman's column was, Amazon's resistance to big publishers using their market power to overprice ebooks. Krugman was on the side of the big publishers for obvious reasons I think. Krugman's own widely-assigned economics texts provide some of the clearest examples of big publishers using monopsony to overprice ebooks. His publisher, presumably with Krugman's support, sells ebooks of these texts for $100 - $200 a copy. A great example of mmonopsony - because students are assigned Krugman's books and therefore don't have choice, Krugman's publisher extracts monopsony profits. This isn't just a little convenient opportunism -- as Krugman surely knows, overinflated textbook prices are a significant burden on many students, who are leaving university with huge debt. Yet, Krugman goes along with this exploitation, and presumably banks very large royalties for himself at student's expense.
I say presumably a couple of times, because I've not seen anything from Krugman explaining or apologizing for the prices of his own books and the way this exploits students.