2008 census
The "Fifth Population and Housing Census of Sudan", of Sudan as a whole, was conducted in April 2008. However the census results of Southern Sudan were rejected by Southern Sudanese officials as reportedly "the central bureau of statistics in Khartoum refused to share the national Sudan census raw data with southern Sudan centre for census, statistic and evaluation." The census showed the Southern Sudan population to be 8.26 million, however President Kiir had "suspected figures were being deflated in some regions and inflated in others, and that made the final tally 'unacceptable'." He also claimed the Southern Sudanese population to really be one-third of Sudan, while the census showed it to be only 22%. Many Southern Sudanese were also said to not have been counted "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 southern Sudanese authorities." The chief American technical adviser for the census in the South said the census-takers probably reached 89% of the population.

2009 census
In 2009, Sudan started a new Southern Sudanese census ahead of the 2011 independence referendum, which is said to also include the Southern Sudanese diaspora. However this initiative was criticised as it was to leave out countries with a high share of the Southern Sudanese diaspora, and rather count countries where the diaspora share was low.