Mankiw Jumps on the Head of Keynes and Then Throws Him Under the Bus: Part 3

Greg Mankiw writes:

A key issue facing the new Obama administration is to what extent the economic stimulus should take the form of spending increases versus tax reduction. One way to think about the issue is the size of the fiscal policy multipliers. The multipliers measure bang for the buck--the amount of short-run GDP expansion one gets from a dollar of spending hikes or tax cuts.

So what are these multipliers? In their new blog, Bob Hall and Susan Woodward look at spending increases from World War II and the Korean War and conclude that the government spending multiplier is about one: A dollar of government spending raises GDP by about a dollar. Similarly, the results in Valerie Ramey's research suggest a government spending multiplier of about 1.4. (Valerie does not present her results in multiplier form, but she emails me this translation: "The right column of figure 5A of my paper shows that for a log change of government spending of 1, log GDP rises by 0.28, implying an elasticity of 0.28. To back out the implied multiplier, we can use
the fact that government spending averages around 20% of GDP. This implies a
multiplier of 1.4.")

By contrast, recent research by Christina Romer and David Romer looks at tax changes and concludes that the tax multiplier is about three: A dollar of tax cuts raises GDP by about three dollars. The puzzle is that, taken together, these findings are inconsistent with the conventional Keynesian model. According to that model, taught even in my favorite textbook, spending multipliers necessarily exceed tax multipliers...

And now, from Mankiw, the jump on the head of Keynes (My emphasis):

My advice to Team Obama: Do not be intellectually bound by the textbook Keynesian model. Be prepared to recognize that the world is vastly more complicated than the one we describe in ec 10. In particular, empirical studies that do not impose the restrictions of Keynesian theory suggest that you might get more bang for the buck with tax cuts than spending hikes.