One thing I couldn’t get into in today’s column, both for the sake of space and comprehensibility for a broad audience, was an explanation of exactly what I meant when I wrote

But we shouldn’t be too hard on Mr. Beck. Similar — and similarly false — claims about the cost of Waxman-Markey have been circulated by many supposed experts.

So let me do that here.

Basic economics says that if we want to discourage a negative externality, like pollution, we need to put a price on that externality. One way is through an emissions tax; an alternative, with very similar economic results, is a system of tradable permits. All this goes back to Pigou; Greg Mankiw has urged economists to join his Pigou Club of those who support externality taxes.

Now, a key point in all this is that the emissions tax or, equivalently, the rent on emissions permits, does not represent a net loss to society. It’s just a transfer from one set of people to another — from the emitters, and ultimately those who buy their products, to whoever collects the taxes or gets the permits, and ultimately whoever benefits from the revenue or rents thus generated. The only net loss is the Harberger triangle created by the reduction in emissions — which has to be set against the benefits of reduced pollution.

And the burden on households from cap and trade depends on what’s done with the rents. In the original Obama plan, the rents would be used to pay for middle-class tax cuts; in Waxman-Markey, many of the permits are initially granted to utilities — but since these utilities’ profits are regulated, many of the rents would end up being passed on to consumers through lower prices.

Enter Glenn Beck. He picked up on a calculation by a conservative blogger who took a guess about the rents on emissions permits and assumed that all of this would amount to a tax on families. (Beck then added his own special sauce by misreporting the blogger’s speculations as a “buried” Obama report.)

Bad stuff. But here’s the thing: how different is this from what, um, Martin Feldstein did a few months ago in an op-ed? Here’s the relevant passage:

The Congressional Budget Office recently estimated that the resulting increases in consumer prices needed to achieve a 15 percent CO2 reduction — slightly less than the Waxman-Markey target — would raise the cost of living of a typical household by $1,600 a year. Some expert studies estimate that the cost to households could be substantially higher. The future cost to the typical household would rise significantly as the government reduces the total allowable amount of CO2. Americans should ask themselves whether this annual tax of $1,600-plus per family is justified by the very small resulting decline in global CO2.

There’s lots of other stuff wrong with that column, but focus on this part. Feldstein knows basic economics, and is well aware that the $1600 number from that report wasn’t an estimate of the net cost to families — and strictly speaking, he didn’t say that it was. But he certainly created that impression, obviously deliberately.

I’d say that Feldstein was channeling Glenn Beck, except that since the Feldstein piece came first, it’s the other way around. So as I said, maybe we shouldn’t be so hard on Mr. Beck.