Large scale migration is a common phenomenon in South Africa where over a third of the population, according to the National Treasury's 2009 Budget Review, currently resides in the nine largest urban areas, the six metropolitan municipalities (Ethekwini, Nelson Mandela Bay, Tshwane, City of Johannesburg, City of Cape Town and Ekurhuleni) as well as Mangaung, Msunduzi and Buffalo City municipalities. This trend is expected to increase in the years ahead. The National Treasury reports that these municipalities face a dual challenge of keeping pace with demand for infrastructure expansion and maintenance while serving the needs of a growing population.