The illegal slave trade was driven by rising demand for plantation products, mainly in Europe, and steady improvements in the productivity of the enslaved population, which in turn increased the value (and therefore the price) of coerced labor. The three major slave economies of the world in the mid-nineteenth century were the U.S., Brazil, and Cuba; their economic expansion was dramatic, and they dominated the world output of cotton, coffee, and sugar, respectively.
The U.S. saw its slave population quadruple between 1790 and 1860 from natural increase rather than the arrival of Africans. By contrast, the people of African descent in Brazil and Cuba experienced either negative or very small positive natural population growth. About 800,000 Africans came into Cuba over the same period that the U.S. enslaved population quadrupled, and about 2.2 million arrived in Brazil. The slave trade became illegal midway through this inflow, and one way of seeing its importance is to recognize that the inflow provided for the Cuban and Brazilian planters what natural increase generated for the U.S. planters–a supply of coerced labor that supported world dominance in a single product. In the U.S. and British Caribbean, relatively few Africans arrived after 1807.
Behind this pattern lay a dramatic increase in the spread between the prices of captives in Africa and slaves in the Americas. As native-born slaves became more productive in the Americas in the nineteenth century, the price of even unskilled individuals rose above $1,000 in the U.S. South, Cuba, and Brazil alike. On the African coast, by contrast, prices declined with the volume of the traffic. On the Congo River in the 1860s, it was possible to buy a young adult male for $30, and after 1807, prices at the point of embarkation were always below $100. Historians have often compared prices on either side of the Atlantic and called the difference "profits," as though transportation and risk did not exist. In fact, illegal slave trading could be extremely costly. Slave vessels avoided established ports and the facilities they offered. Their owners obtained fraudulent (and thus expensive) registration papers. The ships themselves were faster than most other vessels, and often a single venture involved more than one ship, as owners sent out goods and equipment on a different ship as a subterfuge.
Slave trading in its final stage entailed increased risks of capture, more costly delays on the African coast, higher shipboard mortality for the victims, and, most important in financial terms, considerable bribes to officials of the region into which the Africans were introduced. As with the modern trade in illegal drugs, potential profits were high (though they were never simply the price of the enslaved person in the Americas, less the price of the captive in Africa), but so were potential losses. Some of the largest slave traders went bankrupt, including Pedro Blanco, whose name is associated with nearly fifty voyages to Cuba before 1845; he assumed the role of captain, owner, and factor on the coast of Africa –mostly Sierra Leone and Liberia–at different times in his long career.
In some sense, the voyage itself and the captain became much less the center of the overall operation than was the case in earlier centuries. In major markets such as Whydah in Benin and Lagos, Nigeria, it was still possible for a transatlantic vessel to seek captives without prior arrangement, but on most of the coast more elaborate and costly organizational structures were required. The captain's role became less important and the key slave trading personnel operated on shore, on both sides of the Atlantic, rather than on the vessel itself. The major decisions on bringing together (or "bulking") the required number of captives, assembling provisions and equipment, and timing the departure were now made on land.
In the Americas, knowing which officials to bribe and trying to dispose of captives in open-market conditions to maximize returns became more difficult than in the pre-suppression era and required more manpower and a different set of skills. On the voyage itself, captains might find themselves sailing an empty ship out to the African coast, or at least one without the fittings of a slave ship, given that the discovery of such equipment on board increased the risk of conviction in a court of law. Barrels for water (which always occupied by far the largest amount of space on a transatlantic slave vessel), planks for slave decks, irons, a large boiler for cooking, and the provisions themselves were frequently loaded in Africa just prior to departure. In the last few decades of the illegal slave trade, the complete shipment was frequently rushed on board just before leaving for the Americas.