Calculating the statistical dimensions of the slave trade, whether in terms of deaths or number of slaves taken from Africa since the 15th century is not easy. Figures for the Spanish and Portuguese colonies are less reliable than those for North America. The continuation of slavery within Africa in the 19th century after abolition is also poorly documented.


Historical documents containing statistics are not always very reliable. For example, figures for Arab slavery produced by the British government after abolition were inflated as part of the propaganda war against the Arabs in East Africa.

Indeed there remains a great deal of dispute over the figures for the Arab slave trade. One historian produced a total of 17 million slaves, but this is for a period spanning 13 centuries and encompassing trade in North Africa, the North East and South Africa.

A more helpful comparison can be made by looking at the figure for slaves leaving Africa annually for Arab lands from East Africa in the first half of the nineteenth century. This figure exceeds 3,000, compared with the estimate for slaves crossing the Atlantic in the late 18th century at an annual rate of 44,000.


In recent years the slave trade has increasingly been referred to by African Americans as a holocaust (wholesale destruction), and comparisons have been made with the fate of Jews under Nazi rule, as well as the original inhabitants of the Americas at the hands of the first Europeans.

There are a number of movements calling for reparations (financial compensation) to be made by the countries that used to be slave trading nations. These movements are concerned with not just how many people made the journey, but also the impact of the slave trade on population growth over the centuries.


Shipping records are a central source; there are also documents relating to the running of plantations and deeds of ownership. The numbers become clearer in the late eighteenth century as the slave trade reaches its peak and the movement for abolition begins to get under way.

Estimates as high as 50 million have been floated, and for a long time an accepted figure was 15 million, although this has in recent years been revised down.

Most historians now agree that at least 12 million slaves left the continent between the fifteenth and nineteenth century, but ten to twenty percent died on board ships. Thus a figure of 11 million slaves transported to the Americas is the nearest demonstrable figure historians can produce.


A number of slaves would have died at the point of capture and more in course of the journey to the coast. A merchant of Luanda in the late 18th century, Raymond Jalama, observed that nearly half of those captured inland were dead by the time they reached the coast.

The vast majority taken were men and this must have had a huge effect on the population they left behind particularly in a polygamous society.

It has been calculated through computerised projections that the population in Africa in the mid 19th century would have been double what it was had the slave trade not happened - that means that if there had been no slave trade the population of Africa in 1850 would have been 50 million instead of 25 million.


People often became slaves for reasons rooted in local disputes, and wars; or they became slaves as a demonstration of wealth and power on the part of a local ruler. However, enslavement at a local level could often lead to a chain reaction of sales from merchant to merchant ending up at the coast where the final sale resulted in being dispatched across the Ocean.


A large number of people began the journey into slavery as prisoners of war. The Baganda in East Africa, for example, often went to war with their neighbours and took Bunyoro and Basoga people as slaves.

With the rise of a large commercial slave trade, driven by European needs, enslaving your enemy became less a consequence of war and more and more a reason to go to war. This was particularly so in West Africa where, for example, the conflict between the kingdoms of Oyo and Dahomey resulted in prisoners of war being taken as slaves on both sides and then sold on to the coast.


Some people were taken into slavery as a punishment. The crime might be witchcraft, theft, or adultery.

"Every trifling crime is punish'd in the same manner... They strain for crimes very hard in order to sell into slavery." - Francis Moore, Royal Africa Company, writing in the 1730's.


Selling someone into slavery could be a way of discharging a debt.


In Bonny, the largest slave market in the delta of the river Niger many slaves were sold by order of the oracle, Chukwu. The slaves were then sold to merchants, but the oracle was said to have eaten them.


In the area of Senegal, in the 17th century, slaves were given to the king as part of a village's tribute to him, along with brandy, tobacco and cloth.


A large number of people were quite simply kidnapped while going about their everyday tasks. Igbos were particularly wary of being kidnapped and always fortified their houses if they left their villages; but some like Olaudah Equiano were caught unawares.

Elsewhere in West Africa Savanna horsemen would sweep down from the north to launch annual slave raids on agricultural people.

Occasionally Europeans would kidnap people and turn them into slaves, although by doing this they ran the risk of annoying the chain of African middlemen which extended from the interior to the coast.

"It was customary for parties of sailors and coast blacks to lie in wait near the streams and little villages, and seize the stragglers by twos and threes when they were fishing or cultivating their patches of corn." - Richard Drake, recalling life under the command of Captain Fraley of Bristol, whom he served in 1805.


In times of famine children might be sold. Orphans, widows and poor relations were equally vulnerable.


Some slaves were born into slavery in Africa. Traders and captains of slave ships preferred these because they were less trouble, having never known anything but slavery.