When did central banks stop driving up real interest rates in response to inflation?

For monetary policy to be stabilising, nominal interest rates must change more than inflation. When inflation rises, for example, real interest rates must rise to curb demand for goods and services and inflation. If central banks increase nominal interest rates less than inflation, real interest rates fall when there is inflation and this boosts inflation instead of reining it in. Looking at how the Federal Reserve, the Bundesbank then the ECB, the Bank of England and the Bank of Japan have reacted to inflation since the 1970s, we seek to ascertain at what point they started to change nominal interest rates less than inflation. We find that central banks’ key interest rates have no longer reacted to inflation since 2009 in the United States, the United Kingdom, the euro zone and Japan.