Child-headed families are most common in Africa. The HIV/AIDS epidemic has led to many situations where both parents have died and left behind a family of orphans. The children may begin taking over their parent's responsibilities before the last surviving parent has died, when the parent is sick or too weak to work. The eldest children often have to stop going to school and get a job instead in order to gain income for the family. A study by Cornell University in 2005 showed that, in Namibia, the average age of the children acting as parents in their families was 17; some were as young as 9 years old. The number of children heading households in sub-Saharan Africa is reported to be growing. A survey in South Africa in 2006 showed that 122,000 (0.67%) of the country's children were living in child-headed households.