Throughout the 19th and 20th centuries, the use of Standard Italian became increasingly widespread and was mirrored by a decline in the use of the dialects. An increase in literacy was one of the main driving factors (one can assume that only literates were capable of learning Standard Italian, whereas those who were illiterate had access only to their native dialect). The percentage of literates rose from 25% in 1861 to 60% in 1911, and then on to 78.1% in 1951. Tullio De Mauro, an Italian linguist, has asserted that in 1861 only 2.5% of the population of Italy could speak Standard Italian. He reports that in 1951 that percentage had risen to 87%. The ability to speak Italian did not necessarily mean it was in everyday use, and most people (63.5%) still usually spoke their native dialects. In addition, other factors such as mass emigration, industrialization, and urbanization, and internal migrations after World War II, contributed to the proliferation of Standard Italian. The Italians who emigrated during the Italian diaspora beginning in 1861 were often of the uneducated lower class, and thus the emigration had the effect of increasing the percentage of literates, who often knew and understood the importance of Standard Italian, back home in Italy. A large percentage of those who had emigrated also eventually returned to Italy, often more educated than when they had left.