Russ Roberts says something intriguing:

Krugman is a Keynesian because he wants bigger government. I'm an anti-Keynesian because I want smaller government.

Paul Krugman himself has already replied to this. But for me, there's a question here: why is there this empirical correlation between attitudes towards Keynesianism and towards the size of government?

I ask because, as Mark Thoma has said, 'there is no necessary connection between the size of government and Keynesian stabilization policy.'

For example, one could believe that government spending should average (say) no more than 20% of GDP, and yet at the same time favour large discretionary changes in tax or spending to stabilize the economy. 'Small government Keynesianism' is not, prima facie, illogical.

Alternatively, one might favour big government precisely because one is sceptical about the ability of discretionary policy to stabilize the economy, and so a large state is needed to provide automatic stabilizers; Dani Rodrik has made just this point.

So, why are there so few small government Keynesians or big government anti-Keynesians?

One reason, I suspect, lies in public choice economics. It's politically easier for governments to increase spending and borrowing in bad times than to cut them in good times. This means that Keynesian policies contain a tendency for a creep towards big government. Libertarians might regard the cost of this as exceeding the benefit - especially if they agree with Lucas (pdf) that the benefits of stabilization are paltry.

There is, though, something else. Keynes himself was a small(ish) government Keynesian, because he thought goods and labour markets were, to adapt Samuelson's dictum, micro efficient but macro inefficient:

I see no reason to suppose that the existing system seriously misemploys the factors of production which are in use. There are, of course, errors of foresight; but these would not be avoided by centralising decisions. When 9,000,000 men are employed out of 10,000,000 willing and able to work, there is no evidence that the labour of these 9,000,000 men is misdirected. The complaint against the present system is not that these 9,000,000 men ought to be employed on different tasks, but that tasks should be available for the remaining 1,000,000 men. It is in determining the volume, not the direction, of actual employment that the existing system has broken down.

This view, however, is not one we hear much of these days. People who believe markets are micro efficient seem to think they are macro efficient too. And 'Keynesians' are apt to think markets are micro inefficient as well as macro inefficient - or at least they are keener to point out inefficiencies than efficiencies.

And this leaves me with questions to which I honestly don't really know the answers. Is Keynes' 'micro efficient, macro inefficient' view tenable, in which case an interesting position has been lost, perhaps usurped by loud tribalism? Or was he just wrong?