when the central bank increases inflation in order to push unemployment lower it may cause an initial shift along the short run phillips curve but as worker and consumer expectations about inflation adapt to the new environment in the long run the phillips curve itself can shift outward 
this is especially thought to be the case around the natural rate of unemployment or nairu non accelerating inflation rate of unemployment which essentially represents the normal rate of frictional and institutional unemployment in the economy so in the long run if expectations can adapt to changes in inflation rates then the long run phillips curve resembles a vertical line at the nairu monetary policy simply raises or lowers the inflation rate aftermarket expectations have worked themselves out 62in the period of stagflation workers and consumers may even begin to rationally expect inflation rates to increase as soon as they become aware that the monetary authority plans to embark on expansionary monetary policy this can cause an outward shift in the short run phillips curve even before the expansionary monetary policy has been carried out so that even in the short run the policy has little effect on lowering unemployment and in effect the short run phillips curve also becomes a vertical line at the nairu 2