The Volume of the Atlantic Slave Trade: A Synthesis

This article provides a synthesis of the various studies which attempt to quantify the trans-Atlantic slave trade. Since the publication of Philip D. Curtin's pioneering estimates in 1969 (The Atlantic Slave Trade: A Census), there have been numerous revisions of different sectors of the trade, and some scholars – notably J. E. Inikori and James Rawley – have argued that Curtin's global estimate for imports into the Americas is too low. When the revisions are examined carefully, however, it is apparent that Curtin's initial tabulation was remarkably accurate. The volume of exports from Africa across the Atlantic is here calculated at 11,698,000 slaves, while imports into the Americas and most other parts of the Atlantic basin are estimated to have been 9·8–9·9 million slaves – well within range of Curtin's original Census. Many of the revisions are based on shipping data by national carrier, rather than on series derived from estimated imports into different colonies in the Americas. Hence it is possible to substitute new data for much of the eighteenth and nineteenth centuries for many of the import-derived series used by Curtin. The results of these substitutions shift the distribution of slave exports over time but do not affect estimates of the relative scale of the trade by more than 2–3 per cent – hardly significant considering the quality of the data. Inikori and Rawley have failed to distinguish clearly between imports by colony and exports by national carrier; hence their global estimates have resulted in double counting. Further revisions are likely, nonetheless, but until the completion of detailed research comparable to the studies of David Eltis, Roger Anstey, Johannes Postma, and a dozen other scholars it is not possible to estimate the extent of future modifications. In the meantime, the current state of research on the volume of the Atlantic slave trade is summarized in a series of tables which analyse the export trade by time period, national carrier, and coastal origin. It is expected that the present synthesis will challenge historians to examine the impact of the slave trade on different parts of Africa, both to test the regional breakdown of slave exports and to assess the demographic, political, economic and social repercussions on Africa.