Carbon Tax vs Cap-and-Trade. This is boring by now.

If you’ve spent any time in an energy economics class, you have probably seen a slide that shows the essential equivalency of a carbon tax and a cap-and-trade system, at least with respect to their ability to internalize externalities and fix a market failure. However, if you scratch the surface of the simple model used to claim this equivalency and you realize it only works if you have a good knowledge of the supply and demand curves for carbon emissions. (There are other non-equivalencies, too, like where the incidence of the costs falls.)

The equivalency idea is that for a given market clearing of carbon emissions and price, you can either set the price, and get the emissions you want, or set the emissions and you will get the price. As it turns out, nobody really has a good grip on the nature of those curves, and we live in a world of uncertainty anyway, so there actually is a rather important difference: what variable are we going to “fix” about and which one will “float,” carrying  all the uncertainty: the price of the carbon emissions quantity?

I bring this up because today I read a nice blog post by Severin Borenstein which I will reduce to its essential conclusion: A carbon tax is much better than cap-and-trade. He brings up the point above, stating that businesses just are much better able to adapt when they know what the price is going to be, but there are other advantages to a tax.

First, administratively, it is much easier to set a tax than it is to legislate an active and vibrant market into existence. If you’ve lived in the world of public policy, I hope you know that Administration Matters.

Furthermore, legislatures are not fast, closed-loop control systems. They can’t adapt their rules on the fly quickly as new information comes in, and sometimes political windows close entirely, making it impossible make corrections. As a result, the ability to adjust caps in a timely manner is, at best, difficult. This is a fundamentally harder problem then getting people to agree, a priori, on what an acceptable price — one with more than a pinch of pain, but not enough to kill the patient.

So, how did we end up with cap-and-trade rather than a carbon tax? Well, certainly a big reason is the deathly allergy legislatures have to the word “tax.” Even worse: “new tax.” Perhaps that was the show-stopper right there. But it certainly did not help that we had economists (I suspect Severin was not among them) providing the conventional wisdom that a carbon tax and a cap-and-trade system are essentially interchangeable. The latter is not true, unless a wise, active, and responsive regulator, free to pursue an agreed objective is at the controls. So pretty much never.

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