FACTBOX - Caste-based quota system in India

(Reuters) - India's Supreme Court on Thursday upheld the government's decision to increase the number of college places for lower caste students to 49.5 per cent at state-owned educational institutions.

Here are some facts about caste-based reservation in India:

-- Affirmative action started in India in 1950 when government jobs and places in state-funded colleges were allocated to the former "untouchables" of Hindu society and tribal groups.

-- At present, 22.5 percent of government jobs and places in state-funded educational institutions must be allocated to the 'Scheduled Castes' -- mostly the former untouchables of Hindu society -- and tribal groups. They are estimated to make up about 25 percent of India's population.

-- A further 27 percent of government jobs have been set aside for other lower castes and disadvantaged communities, known as "other backward classes" (OBCs). This controversial 1990 decision led to violent student protests in which dozens of upper-caste students set themselves ablaze.

-- With the Supreme Court's latest ruling, the OBCs will also be entitled to an additional 27 per cent of seats in state-funded educational institutions, pushing the total caste-based educational quota in the country to 49.5 percent.

-- Twenty-two percent of seats in the lower house of parliament and state legislatures are reserved for Scheduled Castes and tribal groups.

-- In February 2008, the chief minister of Uttar Pradesh, India's most populous state, tentatively extended lower-caste job quotas into the private sector, the first such policy in India to include private business in the quota system.

-- Supporters of quotas say they are necessary as lower castes have historically had fewer opportunities for decent education.