sentences:  Though difficult to assess, according to the CIA Factbook, in 2008 about 12.8% of the country's population was Muslim; such a lower figure is rejected by Muslim organisations in the country, who claim a figure of 30-35% (which is described as "wishful thinking" by Christian missionaries).According to the Malawi Religion Project run by the University of Pennsylvania, in 2010 approximately 26% of the population was Muslim, concentrated mostly in the Southern Region.Islam arrived in Malawi with the Arab and Swahili traders who traded in ivory, gold and later on slaves beginning from 15th century.