When it comes to the nationalist question, one of the 'fault-lines' in contemporary Catalan politics arises from the fact that Barcelona, with its strong metropolitan economy, continues to attract migrants from all over the world. This contemporary layer of immigration is prone to speak Spanish over Catalan and adds to second and third generation Catalans whose families arrived from other parts of Spain during the 20th century in order to cover the needs of industrial workers which the Catalan economy demanded to prosper; from the latter, some have become proficient in Catalan, others have not.