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.
Occitan language
Today, Occitan is an official language in Catalonia, where a subdialect of Gascon known as Aranese is spoken in the Val d'Aran. Occitan's closest relative is Catalan. Since September 2010, the Parliament of Catalonia has considered Aranese Occitan to be the officially preferred language for use in the Val d'Aran.