With 1,210,193,422 citizens reported in the 2011 provisional Census, India is the world's second most populous country. India's population grew at 1.76% per annum during the last decade, down from 2.201% per annum in the previous decade. The human sex ratio in India, according to the 2011 census, is 940 females per 1,000 males, the lowest since independence. India's median age was 24.9 in the 2001 census. Medical advances of the last 50 years, as well increased agricultural productivity brought about by the "green revolution" have caused India's population to grow rapidly. The percentage of Indian population living in urban areas has grown as well, increasing by 31.2% from 1991 to 2001. Despite this, in 2001, over 70% of India's population continued to live in rural areas. According to the 2001 census, there are twenty seven million-plus cities in the country, with Mumbai, Delhi and Kolkata being the largest.
India's overall literacy rate in 2011 is 74.04%, its female literacy rate standing at 65.46% and its male at 82.14%. The state of Kerala has the highest literacy rate, whereas Bihar has the lowest. India continues to face several public health-related challenges. According to the World Health Organization, 900,000 Indians die each year from drinking contaminated water or breathing polluted air. There are about 60 physicians per 100,000 people in India.
The Indian Constitution recognises 212 scheduled tribal groups which together constitute about 7.5% of the country's population. The 2001 census reported thereligion in India with the largest number of followers was Hinduism, with over 800 million (80.5%) of the population recording it as their religion. Other religious groups include Muslims (13.4%), Christians (2.3%), Sikhs (1.9%), Buddhists (0.8%), Jains (0.4%), Jews, Zoroastrians and Bahá'ís. India has the world's third-largest Muslim population and the largest Muslim population for a non-Muslim majority country.
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".