Yes, it would be useful to do a more systematic study of fiscal austerity, but the Keynesians don’t seem to know how to do so. All I see are cross sectional studies that mix together countries with an independent monetary policy, with those that lack an independent monetary policy (like the eurozone members.) Mark Sadowski did a regression with only those countries having an independent monetary policy, and found the effect went away. No correlation between austerity and growth. This objection to Krugman’s graphs has been made over and over again, but he never responds.
Simon Wren-Lewis also gets the GDP growth data wrong, in a way that makes austerity look worse. He claims that RGDP growth was 2.3% in 2012 and 2.2% in 2013 (the year of austerity in the US.) But that’s annual y-o-y data, and since the austerity began on January 1st 2013, you need Q4 over Q4 data. In fact, RGDP growth in 2012, Q4 over Q4, was only 1.67%, whereas growth in the austerity year of 2013 nearly doubled to 3.13%.
Wren-Lewis says “other stuff happens.” Yes, but the “other stuff” that happened in 2013 is exactly what you might expect with aggressive monetary stimulus, whereas the other stuff that happened when Britain saw a couple years of low RGDP growth, was not at all what the Keynesian model predicts. The British growth slowdown was a productivity story (their job creation is more impressive than the US), and productivity slowdowns suggest supply-side factors (declining North Sea oil output, a structural shift from high compensation City jobs to low compensation service sector jobs, etc.)
Do I need to tell you that is from Scott Sumner? I would add that the “other stuff” — for some but not all countries — is that the regenerative powers of a market economy are stronger than most Keynesians are willing to let on. And you can buy into the entire Keynesian apparatus (I don’t) and still recognize that most of the time fiscal policy simply isn’t that important.