Paul Krugman has an article that talks about the economics concept of *comparative statics* which involves a bit of calculus. The rough idea is this: suppose we have something that is a function of two economics variables and we are on some level curve: at some point . Now if we, say, hold constant and vary by what happens to the level curve ? The answer is, of course, where is a small error that vanishes as goes to zero; this is just multi-variable calculus and the idea of differentials, tangent planes and partial derivatives. The upshot is that the change in , denoted by is approximately .

It isn’t every day that someone in the mainstream media brings up calculus.

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