9.5% of Gauteng's population of 12.8-million were born outside South Africa.
South Africans are on the move – away from poor, rural towns and provinces to bustling urban hubs in search of decent pay, job opportunities and better services.
The 2011 census results released on Tuesday indicate that those who migrate have a better chance of improving their lot in life.
Although the census does not specifically address "urbanisation", the numbers tell a story of migration and of people flocking to urban centres such as Gauteng.
Reinforcing previous research, a steadily urbanising population complicates the government's decisions on resource allocation. It must balance rural development with demands for increased services that new arrivals place on South Africa's swelling towns and cities.
The rate of growth in the population of Gauteng, as well as that of the Western Cape, has surprised even census officials.
Howard Gabriels, chairperson of the South African Statistics Council, said the rate of growth in these regions had stood out, especially because estimates of population distribution in these provinces had been lower.
Gauteng's population grew by 31% to 12.8-million people by 2011, up from 9.4-million a decade ago.
Biggest influx
By 2007 it had overtaken KwaZulu-Natal as the most populous province, according to Statistics South Africa. Gauteng's share of the population rose to 23.7% in 2011.
KwaZulu-Natal's share had remained relatively constant, at about 21%, but fell to 19.8% in 2011.
Meanwhile, the Western Cape's population has grown by about 29% in the past decade, from 4.5-million to 5.8-million, and it is the country's fastest-growing province, according to statistician general Pali Lehohla.
Migration to these provinces has also been marked. Gauteng has had the biggest influx at more than a million people since 2001 and the Western Cape has had more than 300 000.
Financially embattled provinces, namely the Eastern Cape and Limpopo, have experienced the highest outflows, losing about 280 000 and 15 3000 people respectively.
North West and Mpumulanga have had positive inflows of people.
Statistics South Africa notes that North West's highest migration interaction is with Gauteng, although it has gained fewer people from the province – about 75 000 – than it has lost to the country's economic heart: about 103 000.
North West is home to South Africa's platinum mining industry, which, despite recent strife, has been a boon for economic activity in the region.
More about the flows of people from rural to urban areas is likely to be revealed when Statistics South Africa releases detailed data at the provincial and municipal levels.
Urbanisation is difficult to measure because it is happening constantly, according to Thuthukani Ndebele, researcher at the South African Institute for Race Relations.
He said migration figures suggested that the population not only sought jobs, but better services such as health and education.
Growth rates
The institute's research reveals that the five fastest-growing urban areas in 2011 were Polokwane (31.5%), Rustenburg (26.6%), Vanderbijlpark (21.2%), Nelspruit (20.8%) and Ekurhuleni (17.2%).
There were a number of reasons for the growth rates, measured as the proportional change in the population between 2001 and 2011, Ndebele said, and increases in the population could be coming off a relatively low base. A number of these places, particularly Polokwane, are surrounded by rural areas indicating that people want to move to the nearest centres to access jobs and services.
For many individuals looking to move an important consideration would simply be the closest "next best place", he said. This could explain the high inflows of people from the Eastern Cape to the Western Cape, with the latter representing the closest province offering more opportunity and services.
Last year, in its local government budgets and expenditure review, the treasury flagged the difficulties that rural-urban migration was creating for service delivery and governance.
"In more rural jurisdictions, the out-migration of individuals to urban areas has been accompanied by falling average household sizes," the treasury said in the review. "This reduces the number of persons reached by each household service connection and simultaneously added to backlogs in the urban centres."
In larger urban areas, it said, the "process of rapid population growth and falling household size extended the service delivery challenge facing these municipalities".
The effect of immigration on rising urban populations could also not be ignored, said Ndebele. "Immigrants go straight to urban economic hubs."
Vulnerable
It is difficult to measure immigrant numbers, given that many are not recorded. According to the census data, 9.5% of Gauteng's residents were born outside South Africa and 7.4% are not South African citizens.
Trevor Manuel, minister in the presidency in charge of national planning, has acknowledged this difficulty. "People who are vulnerable and feel themselves living in the twilight tend not to declare and it wouldn't be a uniquely South African problem."
Individuals who want to migrate to urban centres such as Gauteng are likely to see an improvement in their lives, the census data shows. The average household income in Gauteng is more than R156 000 a year, or about R13 000 a month, whereas in the Western Cape it is about R143000 per year, or R11 900 a month.
Limpopo remains the province with the lowest average annual household income at R57 000, or about R4 750 a month. The Eastern Cape follows Limpopo, with an average household income of about R65 000 per year, or about R5 400 a month.
The census reinforces South Africa's gloomy unemployment numbers, although Gauteng and the Western Cape reveal lower rates of unemployment.
It puts the national unemployment rate at 29.8%, slightly higher than the figures in the last 2011 quarterly labour force survey, which placed unemployment at 23.9% in the fourth quarter of 2011. The survey is South Africa's official source of labour market statistics.
Expanded definition of unemployment
When discouraged work seekers are counted, which is known as the "expanded definition of unemployment", the census puts the unemployment rate at 40% as against the survey's 35.4%.
Statistics South Africa said the survey was a better measure of unemployment.
The reference period for employment in the census was fixed at October 9 2011. In contrast, the labour force survey uses a moving reference period of three months. The survey, therefore, included people who were employed during the course of every month in the October-to-December quarter, whereas the census only includes those employed in the first week of October.
In addition, the household questionnaire used in census 2011 to collect labour market information was not intended for persons who spent census night in institutions or were transient.
"To the extent that these groups included employed persons, their labour market status would not be known, because they were only required to complete a shorter questionnaire, which excluded labour market questions," said Statistics South Africa.