This document discusses Phillip's curve and the natural rate of unemployment. It notes that in the short run, there is an inverse relationship between unemployment and inflation depicted by Phillip's curve. However, in the long run Phillip's curve becomes vertical as inflation increases due to rising expectations. The natural rate of unemployment (NAIRU) is the rate below which inflation rises, as workers demand higher wages. The document argues the NAIRU theory suggests governments should not try to lower unemployment through demand policies, as that would only cause inflation. However, the NAIRU concept is criticized for lacking empirical evidence and for being against Keynesian demand management.