The average monthly wage hike rate among big companies in Japan has topped 5 percent for the first time since 1991, when the Asian nation experienced an asset-inflated bubble economy, the country’s largest business lobby said Monday. The rate, including regular salary increases and base pay rises, averaged 5.58 percent, the survey by the Japan Business Federation showed, as private firms try to safeguard the lives of their employees from sharp price hikes at home. The average increase in monthly wages by companies responding to the organization, known as Keidanren, was 19,210 yen ($135), the h…