in North East India. According to the provisional results of 2011 census of India, Tripura has a population of 3,671,032 with 1,871,867 males and 1,799,165 females. It constitutes 0.3% of India's population. The sex ratio of the state is 961 females per thousand males, higher than the national ratio 940. The density of population is 350 persons per square kilometre. The literacy rate of Tripura in 2011 was 87.75%, higher than the national average 74.04%, and third best among all the states. Tripura ranked sixth in Human Development Index (HDI) among 35 states and union territories of India, according to 2006 estimate by India's Ministry of Women and Child Development; the HDI of Tripura was 0.663, better than the all-India HDI 0.605. In 2011, the police in Tripura recorded 5,803 cognisable offences under the Indian Penal Code, a number second only to Assam (66,714) in North East India. The crime rate in the state was 158.1 per 100,000 people, less than the all-India average of 192.2. However, 2010 reports showed that the state topped all the states for crime against women, with a rate of 46.5 per 100,000 people, significantly more than the national rate of 18. Ethnic groups According to the 2001 census of India, Bengalis represented almost 70 per cent of Tripura's population while the Tripuri population amounted to 30 per cent. The state's "scheduled tribes", recognised by the country's constitution, consist of 19 ethnic groups and many sub-groups, with diverse languages and cultures. In 2001, the largest such group was the Kokborok-speaking Tripuris, which had a population of 543,848, representing 17.0 per cent of the state's population and 54.7 per cent of the "scheduled tribe" population. The other major groups, in descending order of population, were the Reang (16.6 per cent of the indigenous population), Jamatia (7.5 per cent), Chakma (6.5 per cent), Halam (4.8 per cent), Mog (3.1 per cent), Munda (1.2 per cent), Kuki (1.2 per cent) and Garo (1.1 per cent). Languages The official languages of the state are Bengali, English and Kokborok (Tripuri). Bengali is the most widely spoken language, while Kokborok is the most prominent language among the Tripuri people. Other minority languages such as Mog, Odia, Bishnupriya Manipuri, Manipuri, Halam, Garo and Chakma belonging to Indo-European and Sino-Tibetan families are spoken in the state. Thadou, a nearly extinct language, was spoken by only four people in one village as of 2012.