What Happened to the Phillips Curve?

What Happened to the Phillips Curve?: "truth be told, the Phillips Curve has not worked well outside
America. Economists Doug Staiger, Mark Watson, and Jim Stock pointed out in the _Journal of Economic Perspectives_ that even in the United States the Phillips Curve relationship was never as strong or as good at forecasting inflation as was taught in intermediate macroeconomics. And only in the United States has there been a relatively stable natural rate of unemployment to serve as a reliable indicator of when demand pressure is about to raise inflation. Elsewhere the causes of rising inflation have
always been too complex to be summarized by simply comparing unemployment to even a semi-stable 'natural rate.'

Thus perhaps the surprising thing is not that Phillips Curve-based
forecasts of inflation have gone awry in the past half decade. Perhaps the surprising thing is that the complicated economic processes determining changes in inflation could be summarized for so long by such a simple relationship as the standard Phillips Curve. In any event one thing is very clear: the simple theory of the relation between inflation and unemployment that economists have peddled for a quarter century no longer works; if economists are to be of any use, they need to come up with a better - and in all likelihood more sophisticated - approach to understanding why inflation rises."