In an interview on The Lessons of the Great Depression

So your point is that even in the context of massive expenditures in a wartime situation, the multiplier effect of government spending on the economy is less than one – ie, it is not a multiplier at all. In other words, fiscal stimulus does not work. I read your WSJ editorial on this. Is that a good way for the layman to understand your arguments? Also this, on the “Voodoo Multipliers" and your September 2009 NBER working paper (most recent version available on the left)?

Yes, those articles refer to this kind of evidence, and I’ve been working more on it, trying to make it more precise. Some economists have argued that in a time of slack the multiple should be bigger, because there’s more capacity to respond to the extra demand. There’s a little bit of evidence that that’s right. A lot of that comes from the build-up in World War Two, because in 1941 the unemployment rate is still around nine per cent, so you can see what is the effect in that environment, in a high unemployment situation, of having a big expenditure increase. (Later in the war, the unemployment rate is close to nothing, so you don’t have that setting.) There’s a little bit of evidence from that that the multiplier is bigger when there’s more slack. But it doesn’t look like the multiplier gets up to one, even when the unemployment rate is nine per cent. It’s getting closer to that, but even then it is not one.

And yet neo-Keynesians – which include White House economics adviser Christina Romer – often cite the number as being 1.5, and you say in your article that the Obama administration is using 1.5 as a basis for its fiscal stimulus policies. How do they come up with that then?

Oh they pulled that out of the air. I have the advantage of having at least a little bit of empirical evidence: as I said, it’s based particularly on military purchases. So even though that evidence is not that great, it’s infinitely better than the alternatives, which are no evidence. I think Valerie Ramey’s work is the best in terms of empirically trying to figure what the effect is of expenditure on the macro-variables. She has focused mostly on the post-World War Two period, but she’s looked somewhat at the earlier part.

So you would put her work among your must-reads?

Since part of the remedy for the current crisis is this fiscal stimulus package –which particularly revolves around this Keynesian multiplier – then Valerie’s work is especially relevant there and is probably the best recent work on that topic that I know of.