This is economic cluelessness reaching some kind of peak:
The point is that relatively good private sector performance has been masked by public-sector cutbacks; this is the opposite of what you usually hear, but that’s no surprise.
This is, of course, the point of cutting back on the public sector during bad times, as Obama was forced to do. Krugman is describing the current upturn that has followed the sequester. Making virtue of necessity is the way of the world. But the incapacity of seeing what a dismal detour all of the stimulus spending actually was is the province of Keynesians. Of course, the fall in public sector spending shows up as a fall in GDP. But that’s a fault of the statistic, not of the policy.
Importantly, the reality described is of a rising private sector that is finally being allowed to recover by cutting back on public spending. For a true equation of economic growth, you should try Y=C+I-G, just for a change. It’s still pretty subdued by this is why “austerity” has become the universal policy, irrespective of what our economic textbooks say.