An estimated 1.4 billion people live in India. In addition to counting them, Indian authorities will also register people's caste affiliation, under the ancient and controversial hierarchical system, by next year.
A comprehensive registration of caste affiliation has not been done in 95 years, since India was under British colonial rule.
The last census was conducted in 2011, when the population was 1.21 billion. Since then, the UN estimates that the country has overtaken China as the world's most populous country.
