Why is the Phillips curve vertical in the long-run?

Question

Why is the Phillips curve vertical in the long-run? What is the relationship between inflation and unemployment in the long-run? Why is this so?

What is the relationship between inflation and unemployment in the long-run? Why is this so?

Answer 1

Because in long-run there is only structural and frictional unemployment which constitute this NAIRU level (which is relatively stable) required for economy to adjust for changes (thus there is no cyclical unemployment).

In the long-run there is no relationship between inflation and unemployment because of money-neutrality in the long-run, thus price level changes and unemployment for long-run are in general unrelated.