Then in the next period, the central bank is in the same position as previously, in terms of its distance from its objective; hence, by hypothesis, the central bank has no incentive to increase its effort to meet the announced target, and the public has no reason to expect it to do so.
In this respect the inflation target is too "forgiving" an objective; failure is not penalized, nor is greater effort demanded. In contrast, under a price-level-targeting scheme, continuing deflation combined with an upward-sloping path for the price-level target causes the size of the price-level gap to increase over time.