In the "African Slave Demography Project," Manning created a demographic simulation of the slave trade to show precisely how declined in West and Central Africa between 1730 and 1850 as well as in East Africa between the years 1820 and 1890 due to slavery.
在「非洲奴隸人口計畫」中，曼寧建立了奴隸貿易的人口模擬，以呈現1730年至1850年間的西非、中非；以及1820年至1890年間的東非，如何受奴隸制所害而衰落 。