the effective use of reserved forest lands. The northern tribes have thus been sheltered from the kind of exploitation that those elsewhere in South Asia have suffered. In Arunachal Pradesh (formerly part of the North-East Frontier Agency), for example, tribal members control commerce and most lower-level administrative posts. Government construction projects in the region have provided tribes with a significant source of cash. Some tribes have made rapid progress through the education system (the role of early missionaries was significant in this regard). Instruction was begun in Assamese but was eventually changed to Hindi; by the early 1980s, English was taught at most levels. Northeastern tribal people have thus enjoyed a certain measure of social mobility. The continuing economic alienation and exploitation of many adivasis was highlighted as a "systematic failure" by the Indian prime minister Manmohan Singh in a 2009 conference of chief ministers of all 29 Indian states, where he also cited this as a major cause of the Naxalite unrest that has affected areas such as the Red Corridor. Tribal classification criteria and demands The criteria presently followed for specification of a community as a Scheduled Tribe are : (i) indications of primitive traits, (ii) distinctive culture, (iii) geographical isolation, (iv) shyness of contact with the community at large, and (v) backwardness. Population complexities, and the controversies surrounding ethnicity and language in India, sometimes make the official recognition of groups as Adivasis (by way of inclusion in the Scheduled Tribes list) political and contentious. However, regardless of their language family affiliations, Australoid and Negrito groups that have survived as distinct forest, mountain or island-dwelling tribes in India and are often classified as Adivasi. The relatively autonomous tribal groups of Northeastern India (including Khasis, Apatani and Nagas), who are mostly Austro-Asiatic or Tibeto-Burman speakers, are also considered to be tribals: this area comprises 7.5% of India's land area but 20% of its tribal population. However, not all autonomous northeastern groups are considered tribals; for instance, the Tibeto-Burman-speaking Meitei of Manipur were once tribal but, having been settled for many centuries, are caste Hindus. It is also difficult, for a given social grouping, to definitively decide whether it is a "caste" or a "tribe". A combination of internal social organisation, relationship with other groups, self-classification and perception by other groups has to be taken into account to make a categorisation, which is at best inexact and open to doubt.