In other words, to maintain the unemployment below the ‘natural’ rate, policy authorities will have to inflate the economy at higher rates in each successive period. This has a major policy implication even if the economy does not operate on the long-run vertical Phillips curve.
Under the ‘rational expectations hypothesis’, as there are no deviations between ‘actual’, and ‘expected’ inflation, both in the short-run and long-run, Phillips curves are treated as being vertical with no trade-off between inflation and unemployment. 13. Another policy related question is the shape of the short-run Phillips curve itself.