From the viewpoint that stresses the socially constructed nature of categories such as ethnicity and race, they are characterized by social boundaries that are constantly negotiated through interaction (Nagel 1994; Jenkins 1997; Barth 1998 (1969)). History suggests that the inflow of newcomers into a society has often been accompanied by a realignment of the relationships between existing groups and the redefining of social categories by various agents. For example, with the influx of the Irish, eastern, southern, and central European immigrants into the United States in the 1800s, the formerly unchallenged category of Whiteness became problematic, as the new white immigrants were defined as different, and furthermore as inferior, to the existing populations of whites (Oakes 1985; Fass 1989). According to Fass (1989):
In the early twentieth century, analysts and journalists emphasized that immigration had become newly problematic because the sources of immigration had changed as Italy, Poland, Russia, and the Balkans replaced the British Isles, Germany, and the Scandinavian countries as the home of the majority of the newcomers. The groups composing the so-called ‘new immigration’ were portrayed as more alien, more transient, from more autocratic societies, less family-oriented, less skilled, less literate. In addition, they were often visibly darker and rarely worshipped any recognizably Protestant God.