THE LOGIC OF THE SIMULATION:

1. A MODEL OF FORCED MIGRATION

The simulation model of the experience of Atlantic slave migration is summarized below in two graphical forms. Both figures show simplified versions of the demographic logic of enslavement and slave trade. Figure A1 treats whole populations at once; Figure A2 gives attention to the age and sex composition of populations.

In Figure A1, each circle represents a distinct population. At the beginning of each period, we assume the existence of discrete groups known as Source and Captor populations (in blue). The Captors enslave some people from the Source population each year. In addition, we assume there are groups who were enslaved earlier: the Domestic slaves (in Africa) and the Export slaves (in the Americas) - these are in yellow. The people taken from the Source population each year are known as Captives (in green). The term "captives" refers to persons in the high-mortality period of the first year following their enslavement, after which they become "slaves." Captives undergo an initial mortality, and are then divided into those retained for local use as Domestic slaves, and those intended for export from the region. The latter group undergoes an additional mortality (corresponding to the Middle Passage). (The deaths from these two experiences are shown in red.) In the meantime, all of these populations experience normal births and deaths. At the end of each cycle of enslavement, the surviving Captives are added into the Domestic and Export slave populations, and the next cycle of enslavement begins.

Figure A1

In Figure A2 much of the same information is presented, but with additional details on age and sex in each population. As before, we assume the existence of discrete groups known as Source and Captor populations (in blue). In addition, we assume that there are groups who were enslaved earlier: the Domestic slaves (in Africa) and the Export slaves (in the Americas) - these are in yellow. Note that the Domestic slaves are primarily female while the Export slaves are primarily male. The people taken from the Source population each year are known as Captives (in green) - they are mostly young adults, both male and female. Figure A2 does not show their mortality in transit, but it does show the difference between those who will become Domestic slaves (mostly young adult females) and those who will become Export slaves (mostly young adult males).

Figure A2

2. THE SIMULATION

The simulation consists of a computerized implementation of the qualitative model summarized above. This simulation of the demography of African migration through slave trade and slavery enables the user to project the effects of various conditions on the size and composition of the populations involved. The procedure relies on standard demographic techniques: it approximates a continuous analysis of population change by dividing the populations into five-year age groups and assuming that all events take place at the midpoint of five-year periods.