This is because our research suggests that it takes 12 to 18 months for changes in interest rates to have most of their impact on output, and 18 to 24 months to have most of their impact on prices. Of course, there is always uncertainty about the lags involved, and I'll have more to say about this later on.
To be sure, there will always be times when there are large swings in relative prices in the economy energy prices being a good example. Under inflation targeting, the objective is not to try to offset or stifle these relative price movements.