Paul Krugman is scathing towards people he refers to as “policy entrepreneurs”, non-economists who offer policy advice about economic issues, either to politicians or to the general public. Here’s a quote:

As far as I can tell, the attitude of policy-minded intellectuals to economics is pretty much unique. Many people have opinions about legal matters or about defense policy; but they generally accept that a fair amount of specialized knowledge is necessary to discuss these matters intelligently. Thus a law degree is expected of a commentator on legal affairs, a professional military career or a record of study of military matters is expected of a commentator on defense, and so on.

Paul Krugman, Pop Internationalism (1996)

I’m ambivalent about this. On the one hand, he’s right, I think: non-economists feel more comfortable in commentating on economic policy than non-lawyers feel in commentating on legal issues (for example). Krugman’s criticism is specifically directed towards commentators who get basic things wrong (eg. the S-I=X-M identity), or whose arguments are internally inconsistent (they lack a model), or whose arguments are not supported by the evidence. He’s quite justified, I think, in being frustrated by these things. Imagine being a legal scholar and confronting legal policy commentators who were indifferent between something as basic as the division between judicial and legislative powers, and reacted with hostility when you pointed out their ignorance.

On the other hand, this sort of attitude, if taken too far, can serve to make economic policy a no-go zone for non-economists. I’m not sure this is a good thing.