European Dutch remained the literary language until the start of the 1920s, when under pressure of Afrikaner nationalism the local "African" Dutch was preferred over the written, European-based standard. In 1925, section 137 of the 1909 constitution of the Union of South Africa was amended by Act 8 of 1925, stating "the word Dutch in article 137 [...] is hereby declared to include Afrikaans". The constitution of 1983 only listed English and Afrikaans as official languages. It is estimated that between 90% to 95% of Afrikaans vocabulary is ultimately of Dutch origin.