Slate Magazine developed a terrifc graphic that shows the ever-increasing number of slave ships between Africa and America between the 16th and 19th centuries.
Here's the way it works:
"This interactive, designed and built by Slate’s Andrew Kahn, gives you a sense of the scale of the trans-Atlantic slave trade across time, as well as the flow of transport and eventual destinations. The dots—which represent individual slave ships—also correspond to the size of each voyage. The larger the dot, the more enslaved people on board. And if you pause the map and click on a dot, you’ll learn about the ship’s flag—was it British? Portuguese? French?—its origin point, its destination, and its history in the slave trade. The interactive animates more than 20,000 voyages cataloged in the Trans-Atlantic Slave Trade Database."