The reason why the lower unemployment rate was achieved and a bubble has not occurred is because the inflation rate is set as the direct target for monetary policy. Moreover, given the rise in  19  The following publications showed that the structural unemployment rate was in the range of about 3.0-3.5 percent using unemployment-vacancy analysis.
Ministry of Health, Labour and Welfare, Analysis of the Labour Economy 2015, September 2015. Cabinet Office, Annual Report on the Japanese Economy and Public Finance 2015, August 2015. Bank of Japan, "The Bank's View" in the Outlook for Economic Activity and Prices, October 2014.