Ethnocentrism, tribalism, religious persecution, and prebendalism have plagued Nigerian politics both before and after independence in 1960. All major parties have practised vote-rigging and other means of coercion to remain competitive. In the period before 1983 election, a report prepared by the National Institute of Policy and Strategic Studies showed that only the 1959 and 1979 elections were held without systemic rigging. In 2012, Nigeria was estimated to have lost over $400 billion to corruption since independence. Kin-selective altruism is prevalent in Nigerian politics, resulting in tribalist efforts to concentrate Federal power to a particular region of their interests. Because of the above issues, Nigeria's political parties are pan-national and secular in character (though this does not preclude the continuing preeminence of the dominant ethnicities). The two major political parties are the People's Democratic Party of Nigeria and the All Progressives Congress, with twenty registered minor opposition parties.