Mistakenly Mistaken

As is her wont, Meagan McArdle made some kind of a math error which she refused to admit.  Ultimately, however, she did admit that she was wrong mathematically with various caveats. Shortly after her non-magnanimous admission of error, she posted a long list of Paul Krugman's errors. As evidence, of a sort, that all pundits err and to err is human and etc.  The thing is that there is a difference between predicting what will happen and simple division. In other words, her persistent errors of fact are not the equivalent of some errors of fortune telling.