Japan’s biggest labor union decided Friday to demand pay hikes of 5 percent or more next spring, while setting a higher target for small- and medium-sized companies to help bridge the salary gap between firms of different size. The organization’s target, which matches that of this year’s spring wage negotiations, aims to maintain the current momentum of wage growth amid rising prices driven by higher import costs, the Japanese Trade Union Confederation said. The labor union, also known as Rengo, said it wants to realize a pay raise of 6 percent or more for smaller enterprises, as they tend to …