From what I’m hearing, the current defense of Cameron’s austerity policies against people like Martin Wolf, Jonathan Portes, and me runs like this:

1. Austerity works! Look at our low, low rates!

2. Austerity? What austerity?

3. Anyway, America does it too.

So, on the first point: as Portes says, those low rates reflect pessimism about British economic prospects, not optimism about its creditworthiness.

On the second, a couple of things to bear in mind. First, spending as a share of GDP tends to rise in an economic slump even without a change in policy, both because GDP is smaller and because safety-net programs kick in. As a result, UK spending as a percentage of GDP shot up between 2007 and 2009.

What about since then? I’m suspicious of the IMF numbers on potential output, which seem too pessimistic to me. But for what it’s worth, they say that the output gap — the degree to which Britain has been operating below potential — hasn’t changed much since 2009. Given that, here’s what the IMF World Economic Outlook database says about spending:

Also, VAT went up. So the IMF’s measure of “structural balance” shows substantial fiscal tightening:

Yes, Virginia, Cameron/Osborne are sharply tightening fiscal policy in the face of a depressed economy.

Finally, about America — yes! We’re doing a lot of austerity! Not as much as Britain, I think (although the numbers are hard to parse), but when you count in state and local government we’re doing a lot of contraction. But that doesn’t reflect deliberate policy, certainly not on Obama’s part; it reflects deadlock in Washington and the fiscal woes of state and local governments.

The point is that Britain is choosing to emulate both the United States and the troubled nations of Europe when it doesn’t have to — all in the name of an economic theory that was foolish two years ago, and completely discredited now.