Mainstream social scientists have often examined the paired ideas of racial prejudice and discrimination. A common perspective has been one of individual bigots acting out racial attitudes in discriminatory ways. The social norms guiding racial discrimination can be formal or legal, but most norms today are unwritten and informal. Discrimination targeting African Americans and other Americans of color comes from all levels and categories of white Americans. Most are involved in some subtle, covert, or blatant way in creating, reinforcing, or maintaining the racist reality of US society. White government officials and programs have often favored the racial and political-economic interests of white Americans. Researchers have identified a disturbing array of blocking strategies used by white officials to reduce black representation or voting: gerrymandering political districts, changing elective offices into appointive offices, adding new qualifications for office, purging voter-registration rolls, suddenly changing the location of polling places, and creating difficult registration procedures.