Population density map of India.
With an estimated population of 1.2 billion, India is the world's second most populous country. The last 50 years have seen a rapid increase in population due to medical advances and massive increase in agricultural productivity due to the "green revolution". The percentage of Indian population living in urban areas has consistently grown; from 1991 to 2001, India's urban population increased by 31.2%. In 2001, about 285 million Indians lived in urban areas while more than 70% of India's population resided in rural areas. As per the 2001 census, there are twenty seven million-plus cities, with the largest cities being Mumbai, Delhi and Kolkata.
India is home to two major linguistic families: Indo-Aryan (spoken by about 74% of the population) and Dravidian (spoken by about 24%). Other languages spoken in India come from the Austro-Asiatic and Tibeto-Burman linguistic families. Neither the Constitution of India, nor any Indian law defines any national language. Hindi, with the largest number of speakers, is the official language of the union. English is used extensively in business and administration and has the status of a 'subsidiary official language;' it is also important in education, especially as a medium of higher education. In addition, every state and union territory has its own official languages, and the constitution also recognises in particular 21 "scheduled languages".
As per the 2001 census, over 800 million Indians (80.5%) were Hindu. Other religious groups include Muslims (13.4%), Christians (2.3%),Sikhs (1.9%), Buddhists (0.8%), Jains (0.4%), Jews, Zoroastrians and Bahá'ís. Tribals constitute 8.1% of the population. India has the third-highest Muslim population in the world and has the highest population of Muslims for a non-Muslim majority country.
India's literacy rate is 64.8% (53.7% for females and 75.3% for males). The state of Kerala has the highest literacy rate at 91% while Bihar has the lowest at 47%. The national human sex ratio is 944 females per 1,000 males. India's median age is 24.9, and the population growth rate of 1.38% per annum; there are 22.01 births per 1,000 people per year. Though India has one of the world's most diverse and modern healthcare systems, the country continues to face several public health-related challenges. According to the World Health Organization, 900,000 Indians die each year from drinking contaminated water and breathing in polluted air. There are about 60 physicians per 100,000 people in India.