Slaving voyages accounted only for between 4 and 9 ships out of every 100 leaving Bristol in the 18th century (9% or less). Each slaving voyage tied up a lot of money for at least a year, in the ship itself, the cargo of trade goods and the costs of manning a ship for a long time. Slave trading was a big financial investment, but large profits could be expected. The amount of money invested in slave trading, rather than the number of ships involved, shows that it accounted for a large part of the shipping trade in Bristol.

In the early 18th century, fitting out a slaving voyage might cost about £4,000 (about £200,000 today). However, investors might make up to £8,000 – a profit of 100% (about £400,000 today). Usually profits were much lower than this, at about 10% or less by the late 18th century. This level of profit still compared well with most other investment opportunities. Although high risks were involved, and investors might lose money, the potential returns on slaving were high. Stocks and shares and government bonds at that time were paying about 4% interest. A successful slaving voyage would pay 8% or 9%. Pictured here is a page from the accounts book of the slave ship the Africa. It shows the owners’ shares in 1774 from the first voyage made by the ship. There were eight owners with equal shares. They were paid in two instalments, and got back less than they invested.

It is usually assumed that to make a profit, a slaving voyage needed to make a profit on each part of the ‘triangular trade ‘. Sometimes, however, the slave ship owners didn’t seem to require the ships to bring home goods on the last part of the voyage from the Caribbean to Bristol. The slave ship the Africa , is an example of this in 1774. The ship’s owners instructed their captain not to wait for a return cargo of sugar from St Vincent in the Caribbean (admittedly they seem to have made a small loss on this venture ). The investors in the slave ship the Juba in 1787 made a small profit despite losing the ship and its cargo of sugar off Ireland, returning from the Caribbean to Bristol. But it is probably true that to make a worthwhile profit, each part of the voyage needed to be profitable.

Link to: Ships and shipping in the section From Bristol to Africa