While the extreme case of a flat Phillips curve is more expositional than real, it may be the case that deviations from the 2% CPI inflation target will be harder to close, in the sense of requiring larger policy changes and larger movements in economic slack, as measured by unemployment and the output gap.
Given that the PTA says we must avoid unnecessary instability in output, interest rates and the exchange rate, and also have regard to the efficiency and soundness of the financial system, this suggests that we should be patient in bringing CPI inflation back to the 2 percent target. This indeed is the approach we have been taking in recent years.