India is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people. India consists of twenty-eight states and nine union territories. It is a home to 17.5 percent of the world's population. The first population census in British India was conducted in 1872. Since 1951, a census has been carried out every 10 years. The census in India is carried out by the Office of the Registrar General and Census Commissioner under the Ministry of Home Affairs, and is one of the largest administrative tasks conducted by a federal government.