AS PART of its quest to end Japan’s 15-year-old deflationary torpor, the Bank of Japan is buying around 70% of all newly issued Japanese government bonds (JGBs). Whether this will boost inflation to the central bank’s target of 2% by the spring of next year remains uncertain: it is barely halfway there. But the vast scale of the purchases has certainly warped the world’s second-biggest sovereign-debt market in ways the Bank of Japan did not foresee.