In 1927, the class of "assimilados" was introduced, creating a separate class of Africans who were required to possess, among others, a fluent command of written and spoken Portuguese. This class remained small, however: even by the early 1970s, the literacy rate had reached only 5%. It has been argued that the Portuguese authorities deliberately withheld education from the African population in an effort to prevent the growth of an independence movement, and that education was provided to a select few in order to isolate them from the general population.