Shinzo Abe's return to the post of prime minister has fueled speculation his stimulus policies will extend the yen's biggest drop since 2005. Domestic companies and the best currency forecasters aren't so sure.

The yen is down 9.9 percent this year and on Wednesday weakened below 85 per dollar for the first time in 20 months following calls by Abe for the Bank of Japan to unleash unlimited monetary easing. That overshoots where large manufacturers said the currency will trade at through March, while the five most-accurate predictors of the yen in Bloomberg Rankings said after Abe's win that it will rebound to 82 by the end of June.

Japan's deflation-plagued economy has contracted 7 percent since 2007 as six prime ministers, including Abe in his first term, failed to reverse the course.