What do you do when things turn out right for all the wrong reasons? Do you laugh? Do you cry? Do you do a bit of both, or none of either? This must be the kind of mental acrobatics that observers of consumer price developments at the Bank of Japan are going through at this particular moment.

A growing body of evidence suggests that Japan's consumer price index will stop declining sometime within what remains of this year. The news is obviously welcome for the BOJ, given that consumer prices have to stop declining before the central bank can go about putting an end to its prolonged policy of "quantitative easing."

Under this policy, huge amounts of excess liquidity are being pumped into private-sector banks' deposits with the BOJ. The policy is increasingly outliving its usefulness and consequently becoming more and more difficult to maintain.