4 billion residents. According to reports, the census will continue through next year and will include the registration of people's social caste under India's ancient and controversial hierarchical system. This marks the first comprehensive caste registration in 95 years, since colonial India was under British rule.
21 billion people. Since then, the United Nations reportedly estimates that India has surpassed China as the world's most populous country. The massive undertaking represents a significant demographic and social data collection effort for the world's most populous nation.