Languages of Catalonia
The main cause of Spanish and Catalan social bilingualism in modern Catalonia was large-scale migration from the rest of Spain during the 20th century, as Catalonia started a significant industrialization which demanded an increased workforce from elsewhere. Spanish has historically been spoken among a minority of civil servants born in other regions in Spain and among segments of the wealthiest bourgeoisie. Spanish has also been spoken as a second language by most Catalans, as it has been the only official language over long periods since the eighteenth century.
Politics of Catalonia
On the other side, Catalan remains the predominant language in middle-class and upper-class urban areas, as well as in the region's rural and small cities population. All in all, Spanish remains the language spoken by a significant portion of Catalans, particularly in working-class areas. For Catalan nationalists this is perceived, in the worst case, as a threat, in the best case, as a challenge to be confronted, because Catalan nationalism is centered on language rather than ethnicity.