Making the slave trade illegal did not immediately bring it to an end, but it did change the way in which the traffic was carried on. It reduced the length of the average voyage, as slave traders sought ships that could outsail naval vessels, but it also increased rates at which captives died. Illegality tended to reduce the prices of captives at the point of purchase on the African coast, but it also increased their cost in the Americas by raising the transportation and distribution costs of getting them to markets in the Americas.
The overall impact of attempts to suppress the slave trade was to reduce the number of people carried off from Africa, as well as to keep the price of the plantation produce at levels higher than would have been the case in the absence of suppression. It was also responsible for the gradual drift southward of the slave trade. Brazil, Angola, and southeast Africa were of far greater relative importance after 1820 than they had been at any time since the mid-seventeenth century. Northern Europe largely disappeared as an organizational base of the traffic, though it continued to supply merchandise and ships.
Other striking features of the last phase of transatlantic slave trading, such as the age and gender shifts and the different ethnic composition of coerced migrants, are less easy to associate with suppression. But whatever the ultimate costs and impact of suppression, presumably no one today would agree with those mid-nineteenth-century observers who argued that attempts to end the trade forcibly were hopeless, that they caused more African deaths than African lives saved from the traffic, and that they should be halted immediately.
Robert W. Woodruff Professor of History