Simon's claim that fiscal austerity has been a disaster reminds me of a big bias in the media - the misuse of the word "cost".

Very often, when the press use the word "cost" to describe a policy, what they really mean is a transfer. For example, the BBC says that "offering four weeks paid paternity leave will cost £150m a year". No, it won't. This is a benefit for working fathers but a cost to their employers. This is a transfer, not a cost. Similarly, the Guardian writes: "A cut in the cap on tuition fees would cost just under £2bn." It might cost universities that, but it'll benefit future graduates. Again, it's a transfer - not a pure cost.

Of course, these might well be bad policies. And there might be all sorts of deadweight costs to transfers or dynamic disincentive effects. Once you've estimated these, you can reasonably describe your estimate as a "cost". What you should not do is claim that a transfer the same as a cost.

You might think I'm being pedantic here. I'm not. For one thing, wibble about "cost" can be used to hide the fact that some policies are a positive benefit. For example, in his interview with Natalie Bennett Nick Ferrari spoke of the "cost" of building houses. Ms Bennett should have replied thus:

There is no cost. It's a net benefit. The government can borrow at 2% but charge rent on the completed houses of 4-5% and have a capital asset to boot. If housebuilding is a cost, how come Bovis and Persimmon this week reported big profits? What's more, there are benefits to future renters who get somewhere to live, and to currently unemployed workers who'll get jobs. The only losers are existing home-owners and landlords who'll see lower gains in future because houses will be less scarce. Net, it's highly likey that housebuilding will be a benefit.

There is, though, something even more pernicious going on, which is where Simon comes in. When he estimates that austerity has cost 5% of GDP, he's using cost in the proper sense - of something that leaves us all worse off than we'd otherwise be. Similarly, when he claims that leaving the EU will cost at least 2.2% of GDP, John van Reenen is using the word properly - though you might disagree on his estimate.

The sums here are huge: 5% of GDP is £85bn - vastly more than the few hundreds of millions "cost" of some Labour policies.

And yet most of the media is much quieter about these genuine costs than they are about the spurious "cost" of other policies. Why?

It's not just because of an explicit Tory bias. Even the BBC talks about cost in the wrong sense. I suspect that two other things are going on.

One is a form of certainty effect. There is rough bi-partisan agreement upon the Exchequer cost of transfers to fathers, students or whoever whereas Simon's estimate lacks such consensus. In the world of "due impartiality", the truth is defined as "what people agree about" rather than what is actually the case. And so the word "cost" is misused.

Secondly, there's the fallacy of the "nation's finances"; politicians and the media routinely use this phrase to mean something utterly different - the government's finances. If you commit this error, then you'll believe the cost to the Exchequer is a cost to the nation - when it is no such thing.

Whatever the origins of the error, though, it is a deeply pernicious one. It tends to present any party wanting to increase borrowing as profligate - as imposing costs upon us. But in fact, the true costs are imposed by the parties that have trashed the economy.

* The error I'm describing isn't confined to the right. Leftists also make it when they talk about the "cost" of tax-dodging. This too is a transfer - from the Exchequer to tax-dodgers.