Textbooks get out of date and need revision in the light of recent data or events. Some textbooks are exposed as being just plain wrong and should be re-written completely. Obviously authors in the latter category are reluctant to admit that their textbook is not an adequate description of the way – for example, the economy works – and so they not only resist updating their offering but they also defend it against all the evidence. Anyway, after reading Paul Krugman’s most recent attempt to come to grips with Modern Monetary Theory (MMT) I concluded that it was way past the date that he should be rewriting his macroeconomics textbook. Otherwise he is misleading the students who are forced to use it in their studies. So Paul, its time to update your textbook.