Despite progress made under "Abenomics," Japan's medium-term economic outlook is for growth that is actually weaker than during the nation's period of deflation, according to the International Monetary Fund.

The assessment reflects disappointing levels of business investment and slower than expected progress in reforming the labor market, said Giovanni Ganelli, a Tokyo-based economist at the IMF who helped compile the fund's annual review of Japan.

Policies in place now point to expansion stuck at around 0.65 percent from 2018 to 2020, versus an average of 0.9 percent from 2000 to 2012, when Japan was locked in a deflationary funk.