An estimated 15 million Africans were transported to the Americas between 1540 and 1850. To max. their profits slave ships carried as many slaves as was physically possible. A House of Commons committee in 1788 stated that one slave-ship, The Brookes, was originally built to carry a maximum of 451 people, but was carrying more than 600 slaves from Africa to the Americas.
Slaves were chained together by their hands and feet and had little room to move. Only about half of the slaves from Africa became effective workers in the Americas. Many slaves died during the journey from diseases such as smallpox and dysentery. Others committed suicide by refusing to eat. A lot of the slaves were crippled for life as a consequence they were chained up on the ship.
By the 17th century slaves could be purchased in Africa for only $25 and sold in the Americas for more than $150. After the slave-trade became illegal, prices raised much higher. Even with a death-rate of 50 per cent, merchants could make tremendous profits from the trade.