 Proponents of the slave trade, such as Archibald Dalzel, argued that African societies were robust and not much affected by the trade.In the 19th century, European abolitionists, most prominently Dr. David Livingstone, took the opposite view, arguing that the fragile local economy and societies were being severely harmed by the trade.Because the negative effects of slavery on the economies of Africa have been well documented, namely the significant decline in population, some African rulers likely saw an economic benefit from trading their subjects with European slave traders.