TOKYO :Japan's largest labour union umbrella group is seeing its member unions demand the biggest salary increase in over 30 years as both the government and central bank look for signs of sustainable wage growth to drive the economy. Rengo, which has about 7 million members, said on Thursday its survey found member unions were seeking an average wage hike of 6.09 per cent for this year, the first time in 32 years that they have asked for more than 6 per cent. Its demand could mean another year