Notably, critics on the quantitative easing policy pointed to the useless and harmful accumulation of idle money balance by the banking sector. Yet it may be noted that the effect on the risk premium or the credit spread through ortfolio rebalancing under the zero short-term interest rate is not excluded, though the effect seems to be small (Kimura and Small (2006)).
10  The empirically estimated shadow price reflected the policy duration effect linked to the persistence of deflation under the quantitative easing policy; it reached the bottom (the negative value of 6%) in early 2003, when the deflationary expectation reached the peak. It became close to zero, when the quantitative easing policy was expected to be abandoned (Ichiue and Ueno (2006)).