By adopting a negative-interest rate strategy, Bank of Japan Governor Haruhiko Kuroda managed to reverse China’s effort to devalue the yuan against one of its biggest trading partners -- in minutes. A global demand slump has pushed officials around the world to ease monetary policies that result in competitive currency devaluations. As Douglas Borthwick of Chapdelaine & Co. put it, "Japan is basically saying ‘You know what China, we’ve seen what you did and we’re going to match that.’ Now the ball is back in China’s court."