If those studies are based on the fiscal multiplier from government spending in its entirety I have no doubt they are all over the map or even skewed towards the negative. Not all government spending will have a stimulus effect. I'm not saying that, Keynes didn't say it either. In fact the only ones who are saying it seem to be Austrians in order to "disprove" Keynes.The studies on the fiscal multiplier (a core component of Keynesian economics) are all over the map, but skew toward disproving Keynes' ideas. Furthermore, New classical economics uses just as much math as Keynesian economics, it's just different math. Considering Tom Sargent just won the Nobel prize for work in this area I wouldn't be so quick to dismiss it.