In a speech at the Faculty of Economics at Keio University, BoJ governor said that the aim of QQE is to overcome the prolonged deflation that has gripped Japan. Even if this deflation has been mild, the fact that it has continued for more than 15 years means that its cumulative costs have been extremely large. Looked at in terms of the price level, an annual inflation rate of minus 0.3 percent over a period of 15 years implies that the price level will fall by around 5 percent, but an annual inflation rate of 2 percent over a period of 15 years means that the price level will rise by around 35 percent. Therefore, he thinks it is clear that even mild deflation, if it continues for a prolonged period, will have a large impact on the medium- to long-term decision-making of economic entities.