I'm not sure that the seventies stagflation can be explained away as an external shock (especially since it was US oil drillers who first forced up the price). If it were merely a contingent influence it would not have had the effect that it did.
I agree with Max's point that you have to look at different periods in their specificity. But doesn't that extend to mean that inflation in one period might mean something quite different from inflation in another. In the seventies there was a quite conscious strategy to devalue the wage bill by allowing inflation to take its course, a mistake that allowed industry to raise prices without corresponding productivity increases taking advantage of the loose money supply. Consequently inflation became a cover for stagnation.
-- Jim heartfield