Number Theory: Understanding India's demographic challenge

India’s population is expected to have reached 1.451 billion in 2024, according to the World Population Prospects (WPP) report released by the United Nations on Thursday. India is the world’s most populous country, and will retain that position even in 2100, the report said. What do these projections mean for India’s economic future? Here are four charts which use data from the WPP report and other official sources to put India’s demographic challenge in perspective.