Sorry, Haters: "Derp" Is A Useful Term, And It's Here to Stay

paul krugman

Yesterday, I set off a bit of a storm of economic policy writers using the term “derp.” Gawker’s Max Read says we all sound stupid and demands that stop.

I’m not going to comply, and I have a feeling Nobel Prize winner Paul Krugman isn’t going to either.

“Derp” is a useful term for a concept that never had its own word. Since derp is on the rise, we need a term for it now more than ever.

Read says “derp” is “a word for ‘stupidity.'” Not quite. All derp is stupid, but not everything that is stupid is derp. Until yesterday, I was with Pulitzer Prize winner Nick Confessore on this:

But now we have a rigorous definition of derp, thanks to Prof. Noah Smith. It turns out that derp is actually a Bayesian probability concept:

Bayesian probability basically says that “probability” is, to some degree, subjective. It’s your best guess for how likely something is. But to be Bayesian, your “best guess” must take the observable evidence into account. Updating your beliefs by looking at the outside world is called “Bayesian inference“. Your initial guess about the probability is called your “prior belief”, or just your “prior” for short. Your final guess, after you look at the evidence, is called your “posterior.” The observable evidence is what changes your prior into your posterior.

How much does the evidence change your belief? That depends on three things. It depends on A) how different the evidence is from your prior, B) how strong the evidence is, and C) how strong your prior is…

When those people keep broadcasting their priors to the world again and again after every new piece of evidence comes out, it gets very annoying. After every article comes out about a new solar technology breakthrough, or a new cost drop, they’ll just repeat “Solar will never be cost-competitive.” That is unhelpful and uninformative, since they’re just restating their priors over and over. Thus, it is annoying. Guys, we know what you think already.

English has no word for “the constant, repetitive reiteration of strong priors”. Yet it is a well-known phenomenon in the world of punditry, debate, and public affairs. On Twitter, we call it “derp”.

Which is to say, a policy commentator is “derpy” when his or her (usually his) prior assumptions about the world are so unwarrantedly strong that he is unswayable by evidence. Derpers have a faith-based approach to policy.

Derp is a problem in political debates always and everywhere, but these days it is especially epidemic on the right. Derp is what leads conservatives to insist that hard money is a good idea even as it wrecks the economies of southern Europe; that tax rate cuts are the key to economic growth from any economic and policy baseline; or that Mitt Romney will win the election even when the clear consensus of the polls is that he is behind.

Unfortunately, derp isn’t going away anytime soon. And as long as we have derp, we’re going to need “derp.” Sorry, Max; you’d better get used to it.

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