The population distribution in Tanzania is extremely uneven. The population density varies from 1 person per square kilometre (3 per sq. mi.) in arid regions to 51 per square kilometre (133 per sq. mi.) in the mainland's well-watered highlands to 134 per square kilometre (347 per sq. mi.) in Zanzibar. More than 80 percent of the population is rural. Dar es Salaam is the de facto capital and largest city. Dodoma, located in the centre of Tanzania, is the de jure capital, although action to move government buildings to Dodoma has stalled.
The African population consists of more than 120 ethnic groups, of which the Sukuma, Haya, Nyakyusa, Nyamwezi, and Chagga have more than 1 million members. The majority of Tanzanians, including such communities as the Hehe, Sukuma, and the Nyamwezi, are Bantu speaking groups. Groups of Nilotic or related origin include the nomadic Maasai and the Luo, both of which are found in greater numbers in neighbouring Kenya. Two small groups speak languages of the Khoisan family peculiar to the Bushman and Khoikhoi peoples. Cushitic-speaking peoples, originally from the Ethiopian highlands, reside in a few areas of Tanzania. Other Bantu speaking were refugees from Mozambique.
The population of Africa has grown rapidly over the past century, and consequently shows a large youth bulge, further reinforced by a low life expectancy of below 50 years in some African countries. The population doubled in the period 1982–2009 and quadrupled from 1955–2009, according to United Nations estimates. The total population of Africa is estimated at 1 billion (as of November 2009.)