Krugman insists that the insights of classical macro have been proven accurate:
Portes quotes a three-year-old piece from Niall Ferguson I mercifully missed, ridiculing me as the “man from Econ 101” who believed, foolishly, that huge government deficits could fail to raise interest rates in a depressed economy. Indeed, that is what Econ 101 said – and it has been completely right. Basic IS-LM macro also said that under these conditions printing lots of money would not be inflationary, and that cutting government spending sharply would cause the economy to shrink. All of this has come true.
Simon Wren-Lewis agrees:
We have not, either individually or collectively, decided that the Great Recession implies that some chunk of what we used to teach is clearly wrong and should be jettisoned as a result. Speaking for myself and my second year undergraduate lectures, quite the opposite is the case. As Paul Krugman has pointed out many times, recent developments have in many ways been a vindication of the basic Keynesian model that lies at the heart of any undergraduate macro course. Indeed, I would go even further. The mess we are currently in is due in part to policy makers ignoring this basic macroeconomic analysis. As a result, I teach this stuff with renewed vigour and determination.