According to Census 2011 results, almost half the people living in Gauteng were not born in the province.
The document, a snapshot of the situation in South Africa at midnight on October 9 last year, finds people tend to move into Gauteng from other provinces, or from outside the country.
"Only 56% of people counted in Gauteng during Census 2011 were born there, compared to 94% of people in the Eastern Cape."
The population of Gauteng at the time of the census was just over 5.8-million people.
The percentage of the provincial population born outside of South Africa is also highest in Gauteng, at 9.5%. The next closest is the Western Cape, at 4.7%.
Of the total number of people counted across the country – close to 51.8-million, after adjustments – about 2.3-million (4.4%) declared they were born outside South Africa.
The white population group had the highest percentage (8.5%) of people who were not born in South Africa. Second were Indians or Asians (at 7.3%), and then blacks (3.9%).
The third census undertaken in post-1994 South Africa also reveals some major shifts in population between provinces.
The greatest appears to have been in Gauteng. There were 7.6-million people counted in that region in the 1996 census. This had grown to 9.2-million by 2001, and to 12.3-million last year – an increase of 33.7% percent from 1996 to 2011.
The population of the Western Cape grew by 28.7% – from almost four million to 5.9-million – over the same period.
Mpumalanga grew by 20%; from 3.1-million in 1996, to just over 4.5-million last year.
In contrast, the Free State's population – pegged at 2.7-million in October last year – grew by 1.4% over the 15-year period.
Compared to a national population increase of 15.5% between 1996 and 2011, this suggests people are migrating out of the province.
According to Statistics South Africa officials at the briefing on Tuesday, the latest census had an estimated 14.3% undercount, down from the 17% undercount in the previous (2001) one.
A system of estimation and adjustment was used to arrive at a "true population" figure for the country.
Undercounts of less than 10% are considered to be a good indicator of an accurate census. – Sapa