Anyone who thought Japan was a boring place economically speaking sure got a surprise from Tokyo yesterday. The Bank of Japan cut its benchmark interest-rate target to a range between zero and 0.1%, from 0.1%. It is also rolling out a new round of quantitative easing, whereby the central bank will buy government bonds, short- and long-term corporate debt, exchange-traded funds and even Japan real-estate investment trusts, all in the name of pouring yen into the economy. The zero interest-rate policy of yore is back.

Japan...