Beijing — A rice bag holds nearly all the earthly belongings of Xu Xian He, a 60-year-old migrant worker. He sits at the Beijing West Railway Station, smoking tobacco through a long pipe and waiting for the eight-hour train ride home to Jiaozuo, Henan Province. He’ll visit his wife and his beloved farm for a few days, and then he’ll leave again to find construction work in another city. “I like every place where I can make money,” Xu pointedly tells me through an interpreter. As long as he earns more than farm wages, “I don’t care what city. There’s...