Working-class formation in the United States was considerably complicated by waves of immigration from the mid nineteenth century down to the present. In some cases, the ethnic differences lead to conflict, in others to “ethnically hybrid” cultures based on class. Labor and radical organizations often played an important role in acculturating late nineteenth- and early twentieth-century immigrant workers. The kind of ethic “niches” in earlier industrial occupational structures can also be found in the employment available to immigrants today. By the late twentieth century, union organization was also complicated by shifts in the occupational structure from manufacturing to service jobs, yet much of the meager growth in union organization in recent decades has come in service industries with heavy concentrations of immigrant workers.