Thursday, October 2, 2014

Economic numerology

A few days ago, Paul Krugman made reference in one of his columns to some data compiled by the US Energy Information Administration on trends in energy use over the past few decades. The data touch on the question of how much energy different nations use to generate $1 of GDP. Are we getting more or less efficient in our use of energy? The numbers, as Krugman argued, show we’re generally getting more efficient. Below I’ve listed the numbers for US energy usage from the year’s 2001 through 2011, in sequential order, from left to right, separated by commas, the units being BTUs per dollar of GDP:

8,482.307, 8,459.179, 8,274.763, 8,178.463, 7,944.349, 7,688.294, 7,671.837, 7,543.901, 7,414.716, 7,503.361, 7,328.424

So you see, the amount of energy used to generate each bit of GDP is going down. Same is generally true for other nations. Fair enough. I’m not going to question that.

But isn’t there something fishy about these numbers? The energy units are BTUs, and the final entry says we used precisely 7,328.424 BTUs per dollar of GDP in 2011. There are 7 specific digits reported in this number, implying that we know our energy/GDP figure to an accuracy of 1 part in 10 million. It’s incredibly impressive. Think about that “.424" at the end. It’s not “.425" or “.423" but exactly “.424".

Is this at all meaningful? Of course not. It’s ridiculous. Unfortunately, this kind of illusory accuracy infects economics and finance quite widely. It may not be the most important issue in the world — even writing about it makes me feel like a grumpy old man — but we’d all think more clearly if we paid more attention to the numbers. So, what’s wrong here?    Read the rest in the new collection Bull Market at

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