What was the tonnage carried in the Triangle Trade?
I'm interested in metrics regarding trans-atlantic trade in the era of the sail. The specific timespan doesn't matter. The specific cargo also doesn't matter.
Since you are asking for metrics, I'm not going to comment much in my answer and just give you the metrics I found.
The Middle Passage 1600 - 1800
From PBS The African Slave Trade and the Middle Passage
- Out of the roughly 20 million who were taken from their homes and sold into slavery, half didn't complete the journey to the African coast
- 10 to 12 million Africans were sold into slavery from the 15th through the 19th Centuries..
- Roughly 54,000 voyages were made by Europeans to buy and sell slaves (Middle Passage).
- Over the centuries, between one and two million persons died in the crossing.
From Digital History The Middle Passage
- The trans-Atlantic slave trade was the largest movement of people in history.
- The level of slave exports to the New World grew from about 36,000 a year in the early eighteenth century to almost 80,000 a year during the 1780s. By 1750, slavers usually contained at least 400 slaves, with some carrying more than 700.
Throughout the height of the Atlantic slave trade (1570–1808), slave ships were normally smaller than traditional cargo ships, with most slave ships weighing between 150 and 250 tons. This equated to about 350 to 450 enslaved Africans on each slave ship, or 1.5 to 2.4 per ton. The English ships of the time normally fell on the larger side of this spectrum and the French on the smaller side. Ships purposely designed to be smaller and more maneuverable were meant to navigate the African coastal rivers into farther inland ports; these ships therefore increased the effects of the slave trade on Africa. Additionally, the ships' sizes increased slightly throughout the 1700s; however the number of enslaved Africans per ship remained the same. This reduction in the ratio of enslaved Africans to ship tonnage was designed to increase the amount of space per person and thus improve the survival chances of everyone on board.
The bolded ratio above allows you to convert ship tonnage to yield estimated cargo. The below tables detail date ranges, ship sorties and ship tonnage for vessels involved in the middle passage.
The following tables come from JSTOR
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Characteristics of British Slaving Vessels, 1698-1775
Walter E. Minchinton
The Journal of Interdisciplinary History
Vol. 20, No. 1 (Summer, 1989), pp. 53-81