Strikes at Chinese factories have surged to a seven-year high and are expected to become more frequent as weak global demand forces exporters to cut workers' pay and shut down plants, one rights group and economists say. Exports and factory output in the world's second-largest economy tumbled in May, as looming downturns force the United States and Europe to pare back orders for goods made in China. "We believe that the drop in manufacturing orders and that factory closures will continue," said Aidan Chau, researcher at Hong Kong-based rights group China Labour Bulletin (CLB).