of married couples, unmarried adults, seniors and children. As the simulation progresses, household composition changes with the birth of children, death of members, and the absorption of unsupported members into other households, when there are no remaining adults. This change in household composition is an important indicator of the effect of stressors. Based on the available evidence ( Drimie and Ziervogel 2006 ), a typical household size ranges from 7 to 10 members. Household income sources In contrast to many other countries in Africa, South Africa has a social support system which provides grants of various types to the people. The various types of grants provide the main source of income, sufficient in many cases to support an entire household ( Pronyk 2002 ; Ziervogel et al. 2005 , 2006b ). A significant proportion of the grant money is essentially spent on food. This is followed by transport and medical expenses and for membership fees to various organizations. Three basic types of grants, listed in Table 2 are available. Table 2: Available grants Grant Type Specification Child Support Grant For children under the age of 7. Disability Grant For adults suffering from HIV/AIDS. Not all qualifying adults apply for this grant as there is a social stigma when an individual is known to be infected. Old-age Pension Seniors may receive this grant from the age of 55 for women and the age of 60 for men. Another significant source of income comes from individuals who have found employment, either within