The "unprecedented" monetary easing operation by Bank of Japan Gov. Haruhiko Kuroda has entered its fourth year, but it remains far from clear when the central bank's target of an annual 2 percent inflation — hoisted as a yardstick in the BOJ and Abe administration's bid to bust deflation — will be achieved. Kuroda's initial vow to achieve the goal in two years has since been pushed back — now to "by the first half of 2017." The BOJ chief remains bullish that his policies are having the anticipated results, but Japan's growth is still uneven and fragile. The latest tankan quarterly survey by the bank shows business sentiment has fallen back to levels right after Kuroda's monetary stimulus was launched three years ago.

The cloudy economic prospects are fueling speculation that the BOJ will take additional easing steps — either expanding its massive asset purchases further to pump more money into the economy or increasing the negative interest rate policy that it began in January. But the performance of the past three years points to the limitations of relying on central bank actions alone in fighting deflation. Instead of taking more of the same steps, both the BOJ and the administration should review whether their policies are really effective in achieving what they claim to achieve.

Tapped by Prime Minister Shinzo Abe to take charge of a key component of his "three arrows" to pull Japan out of deflation, Kuroda launched the massive asset purchase program in April 2013 right after his inauguration as BOJ chief. With its annual purchase of ¥50 trillion in government bonds (whose scope was later expanded to ¥80 trillion), the central bank sought to double the nation's monetary base — the new yardstick in its monetary policy — in two years. Kuroda stressed that the BOJ, by demonstrating its commitment to busting deflation, was aiming to raise inflationary expectations of the public and businesses, thereby encouraging them to spend and invest more.