Math, equations, graphs, and the like are often used to convey the appearance of understand and insight. In many cases, no there is no understand or insight; the conveyance is pure illusion; a charlatan is at work (knowingly or unknowingly).
Such is the case with Krugman’s post from last week (upon which I commented here). Don Boudreaux points out a similar, albeit essentially generic, case in this great post.
In my post I use the word “calculation” to represent that which PK is using irrationally. I should have been more clear in that post. What I mean is that PK is using some arithmetic (Don’s word) – behind the scenes, he’s using some kind of macro economic model about how the world might work – to make a point. But the arithmetic (the “calculation”) is not based on anything that has been confirmed to actually represent reality. That is: PK’s model is bogus. (Indeed, essentially ALL macro models are bogus.)