Christine Lagarde wants her staff at the International Monetary Fund to examine what might happen to the global economy when central banks begin to raise interest rates. She's wasting their time.

If Japan has taught us anything, it's that slashing rates to zero and beyond is a lot easier than returning them to normalcy. Japan is on its sixth central bank governor since its bubble imploded in 1990, and like his predecessors, Haruhiko Kuroda is doubling down on quantitative easing. Why? Politicians, bankers, investors and businesspeople alike get addicted to free money all too easily and clamor for more.

Once central banks start embracing assets such as corporate debt, commercial paper, mortgage-backed securities, exchange-traded funds, real-estate trusts and the like, monetary officials tend to get stuck. That's especially so in nations carrying large, and growing, debt burdens.