Specifically, in 2003, Professor Michael Woodford and then IMF economist Gauti Eggertsson further developed Professor Paul Krugman’s theory and formulated a theory for policy measures that would be effective under deflation and the zero lower bound on nominal interest rates.2 They argued that the most important aspect is the management of the expectations of private entities and that, to that end, it is critical for the central bank to make a commitment that future monetary policy will be sufficiently accommodative.
In this context, simply increasing the target amount of quantitative easing or  2  Gauti B. Eggertsson and Michael Woodford, “The Zero Bound on Interest Rates and Optimal Monetary Policy,” Brookings Papers on Economic Activity, 2003, No.1: 139–233. BIS central bankers’ speeches  3  diversifying the range of assets to be purchased would not bring about strong effects.