By the early 19th century, Glasgow was frequently referred to as the second city; and during much of the 20th century it had a population of over one million, larger than that of Birmingham until the 1951 census. For example, the Official Census population for Glasgow was 0.784 million in April 1911; 1.034 million in April 1921; 1.088 million in April 1931 and 1.090 million in April 1951. However, slum clearance in the 1960s led to displacement of residents from the city centre to new communities located outside the city boundaries. This, together with local government reorganisation, resulted in the official population of Glasgow falling sharply. The Glasgow City Council area currently has a population of 600,000 although the surrounding conurbation of Greater Glasgow has a population of 1,199,629. In contrast, the population of the city of Birmingham has remained steady around the one million mark; its central population fell like Glasgow's, but the city boundaries were extended several times in the early 20th century. Occasional claims were made for Liverpool, Birmingham and Manchester.