When the GHMC was created in 2007, the area occupied by the municipality increased from  to . Consequently, the population increased by 87%, from 3,637,483 in the 2001 census to 6,809,970 in the 2011 census, 24% of which are migrants from elsewhere in India, making Hyderabad the nations List of most populous cities in India. , the population density is . At the same 2011 census, the Hyderabad Urban Agglomeration had a population of 7,749,334, making it the List of million-plus agglomerations in India in the country. The population of the Hyderabad urban agglomeration has since been estimated by electoral officials to be 9.1 million as of early 2013 but is expected to exceed 10 million by the end of the year. There are 3,500,802 male and 3,309,168 female citizens—a sex ratio of 945 females per 1000 males, higher than the national average of 926 per 1000. Among children aged  years, 373,794 are boys and 352,022 are girls—a ratio of 942 per 1000. Literacy stands at 82.96% (male 85.96%; female 79.79%), higher than the national average of 74.04%. The socio-economic strata consist of 20% upper class, 50% middle class and 30% working class.. How many years did it take for the population to increase by 3172487 people?