The sociology of immigration involves the sociological analysis of immigration, particularly with respect to race and ethnicity, social structure, and political policy. Important concepts include assimilation, enculturation, marginalization, multiculturalism, postcolonialism, transnationalism and social cohesion.
Global immigration during the twentieth century was particularly rapid during the first half of the century. Due to the emergence of World War I and World War II, European immigrants came to the United States in vast quantities. Particularly following the end of World War I, Americans labeled European immigrants as dangerous to American culture. In 1924, the United States Congress passed the Immigration Act of 1924, which placed strict quotas on immigrants entering the United States.
From the 1960s to 1990s, the stigma labeling immigrants as "job takers" and "criminals" subsided, and instead Americans began to consider immigrants as benefactors to the American economy, culture, and political system. Although the negative labels that immigrants were given, during the first half of the twentieth century, influenced their actions in society and self-perceptions (known as labeling theory in sociology), immigrants now began to assimilate more easily into society and form strong social networks that contributed to their acquisition of social capital—the "information, knowledge of people or things, and connections that help individuals enter, gain power in, or otherwise leverage social networks".
Sociologists have studied immigration closely in the twenty-first century. Compared to the majority of European immigrants entering the United States during the early twentieth century, the twenty-first century witnessed the arrival of immigrants predominately from Asia, the Middle East, and Latin America. From 2000 to 2001, sociologists have paid particular attention to the costs and benefits of the new diversified immigration population on American institutions, culture, economic functions, and national security. After the attacks on the World Trade Center on September 11, 2001, sociologists closely analyzed the symbolism of increased anti-immigration rhetoric, directed at Middle Eastern immigrants, stemming from Americans. Structural functionalists theorists have also studied the effects of mass migration—resulting from wars, economic insecurity, and terrorism—on the social institutions of host nations, international law, and assimilation rates. Additionally, sociologists exercising social conflict theory have analyzed, in particular, labor market conflicts resulting from increased marketplace competition due to the rise in competition between immigrants and native workers for jobs and social mobility. Because rates of global immigration are continuing to increase, the field of sociology has a particular interest in monitoring twenty-first century immigration as it relates to the foundational theories of symbolic interactionism, social conflict, and structural functionalism.