In essence, the slave trade and the institution of slavery were commercially based. One of the best examples of the importance of financial considerations in the slave trade is the case of the slave ship the Zong, 1781:
Insurance had been taken out on the lives of the slaves as cargo before the ship left Liverpool. The insurer agreed that for any cargo that had to be thrown overboard, meaning the slaves had died, they would pay out. During the journey a number of sick slaves were taken on deck, chained together and thrown overboard. On the ship's return, an insurance claim was made. The publicity over the case did not concern the loss of life, but the possibility that the claim was fraudulent. This ruling emphasised the racial prejudice at the heart of the slave trade and the British establishment.
The prime motivation on the middle passage was to transport as many slaves as possible to the auctions in the West Indies, alive. The buying and selling of slaves meant that family life was precarious. A husband, wife and child had little chance of staying together. Slaves were regarded as individual auction goods.
To extract as much work from slaves as possible on the plantations, they were often beaten or worse. As slaves were property, bought and paid for, they were valuable. On the other hand, they were cheap enough to work, or beat to death. This was known as wastage.
In the British Caribbean, estates were managed for absentee owners by overseers. Their main interest was to amass profits so they could gain a foothold in the plantation economy.
Owners and overseers were aware of the risks to their own health from a lengthy stay in the West Indies. They wanted to make money as quickly as possible and return to Britain to enjoy their wealth.
Saving money on food kept costs down. Long working hours increased production. But poor diet and exhaustion raised the slave death rate. Owners wanted to keep 'their property' in a fit condition to work. The death of a slave meant buying a replacement.
By the 18th century, planters were utterly reliant on the labour of enslaved Africans. The Caribbean population was increasingly African. They were also still reliant on the Atlantic slave trade. Slaves were dying faster than they reproduced.
By 1750, 800,000 Africans had been shipped, but the slave population stood at only 300,000. This was due to very high mortality rates. For most of the 1700s there was a continuous supply of replacement slaves, and their price was low enough that the usual policy was to drive the slaves to work as long as possible.