The Fifth Population and Housing Census of Sudan for Sudan as a whole, was conducted in April 2008. The census counted the Southern Sudan population at 8.26 million; However, Southern Sudanese officials rejected the census results of Southern Sudan because “the central bureau of statistics in Khartoum refused to share the national Sudan raw census data with the southern Sudan centre for census, statistics and evaluation.”
In addition, President Kiir “suspected figures were being deflated in some regions and inflated in others, and that made the final tally ‘unacceptable’.” He claimed that the Southern Sudanese population actually constituted one-third of that of Sudan, though the census showed it to be only 22%.
Many southern Sudanese were also said to have been uncounted “due to bad weather, poor communication and transport networks, and some areas were unreachable, while many southern Sudanese remained in exile in neighbouring countries, leading to ‘unacceptable results’, according to southern Sudanese authorities.” The chief American technical adviser for the census in the south said that the census-takers probably reached only 89% of the population.
In 2009, Sudan initiated a Southern Sudanese census ahead of the 2011 independence referendum, which would also include the South Sudanese diaspora; however, this initiative was criticised for leaving out countries with a high share of the South Sudanese diaspora, rather counting countries where the diaspora share was low.