 He argued that the slave trade was part of what he termed the "primitive accumulation" of capital, the 'non-capitalist' accumulation of wealth that preceded and created the financial conditions for Britain's industrialisation.The demographic effects of the slave trade is a controversial and highly debated issue.Although scholars such as Paul Adams and Erick D. Langer have estimated that sub-Saharan Africa represented about 18 percent of the world's population in 1600 and only 6 percent in 1900, the reasons for this demographic shift have been the subject of much debate.