The summary "Deflation and money" by Hiroshi Yoshikawa, Hideaki Aoyama, Yoshi Fujiwara, and Hiroshi Iyetomiof says:
Deflation and money, Vox EU: Deflation is a threat to the macroeconomy. Japan had suffered from deflation for more than a decade, and now, Europe is facing it. To combat deflation under the zero interest bound, the Bank of Japan and the European Central Bank have resorted to quantitative easing, or increasing the money supply. This column explores its effectiveness, through the application of novel methods to distinguish signals from noises.
...all in all, the results we obtained have confirmed that aggregate prices significantly change, either upward or downward, as the level of real output changes. The correlation between aggregate prices and money, on the other hand, is not significant. The major factors affecting aggregate prices other than the level of real economic activity are the exchange rate and the prices of raw materials represented by the price of oil. Japan suffered from deflation for more than a decade beginning at the end of the last century. More recently, Europe faces a threat of deflation. Our analysis suggests that it is difficult to combat deflation only by expanding the money supply.