In the account of the history of macroeconomic thought I gave here, the New Classical counter revolution was both methodological and ideological in nature. It was successful, I suggested, because too many economists were unhappy with the gulf between the methodology used in much of microeconomics, and the methodology of macroeconomics at the time.
There is a much simpler reading. Just as the original Keynesian revolution was caused by massive empirical failure (the Great Depression), the New Classical revolution was caused by the Keynesian failure of the 1970s: stagflation. An example of this reading is in this piece by the philosopher Alex Rosenberg (HT Diane Coyle). He writes: “Back then it was the New Classical macrotheory that gave the right answers and explained what the matter with the Keynesian models was.”
I just do not think that is right. Stagflation is very easily explained: you just need an ‘accelerationist’ Phillips curve (i.e. where the coefficient on expected inflation is one), plus a period in which monetary policymakers systematically underestimate the natural rate of unemployment. You do not need rational expectations, or any of the other innovations introduced by New Classical economists.
No doubt the inflation of the 1970s made the macroeconomic status quo unattractive. But I do not think the basic appeal of New Classical ideas lay in their better predictive ability. The attraction of rational expectations was not that it explained actual expectations data better than some form of adaptive scheme. Instead it just seemed more consistent with the general idea of rationality that economists used all the time. Ricardian Equivalence was not successful because the data revealed that tax cuts had no impact on consumption - in fact study after study have shown that tax cuts do have a significant impact on consumption.
Stagflation did not kill IS-LM. In fact, because empirical validity was so central to the methodology of macroeconomics at the time, it adapted to stagflation very quickly. This gave a boost to the policy of monetarism, but this used the same IS-LM framework. If you want to find the decisive event that led to New Classical economists winning their counterrevolution, it was the theoretical realisation that if expectations were rational, but inflation was described by an accelerationist Phillips curve with expectations about current inflation on the right hand side, then deviations from the natural rate had to be random. The fatal flaw in the Keynesian/Monetarist theory of the 1970s was theoretical rather than empirical.