When a conservative central bank describes its policy shift as "massive", there can be little doubt about the revolution in Japanese monetary policy.
This enormous shift will fascinate the rest of the global central bank community, as Japan's feeble economic performance is often seen as the canary in the coal mine – a warning of the consequences of repeated policy mistakes.
The immediate response on Thursday from two of the largest – the European Central Bank and the Bank of England – showed a complete lack of international co-ordination. The BoE kept policy unchanged and issued no statement, while Mario Draghi, ECB president, said his institution was "ready to act" but did not feel that any additional monetary stimulus was yet warranted.
(Read More: The Buck Does Not Stop With ECB: Draghi)
The reluctance to follow Japan's lead partly reflects the special circumstances of Japan's economy.
Unlike any other large economy, Japanese nominal gross domestic product – the cash value of money spent on goods and services – was lower in 2012 than 20 years earlier, as gains in the volume of output were offset by falling prices.
The victory of deflation over Japan's moderately loose monetary policy has often been attributed to a conservatism in Tokyo not shared by other central banks since the 2008 financial crisis.
Most European and American central bankers feel Japan is catching up with their steely efforts to maintain low, but positive, inflation rates during the recent years of sub-par economic performance. Although nominal GDP growth in the US, eurozone and the UK has been disappointing over the past three years, deflation has been conspicuous by its absence.
(Read More: Bank of Japan Policy Is Huge, Risky Experiment)
So confident is the Federal Reserve that it has now succeeded in shifting US sentiment that John Williams, the dovish president of the San Francisco Fed, this week predicted it would start reducing its money-printing and asset-purchasing operations this summer. "If all goes as hoped, we could end the purchase program some time late this year," he added.