A Pacific free trade pact would give a big boost to Japan's economic growth and individual incomes, according to an International Monetary Fund economist.

"It could be annually between 0.2 to 0.3 percent (percentage point) per year as an additional impact on growth," Luc Everaert, head of the IMF's Japan Division, said in a recent interview, referring to the impact that conclusion of the Trans-Pacific Partnership would have on the annualized real growth rate.

"If you accumulate this over a 10-year period, that adds up of course to a significant increase. This is only the pure effect of the TPP," said Everaert, who also serves as assistant director of the Asia and Pacific Department of the Washington-based lender.