The effects of the proclamations ordered by British governor of Virginia Lord Dunmore in November 1775 and British general Sir H
enry Clinton in 1779 on the enslaved population in Virginia are carefully analyzed in articles by Sylvia Frey and Cassandra Pybus. Pybus article is titled "Jefferson's Faulty Math," referring to Thomas Jefferson's claim that about 30,000 Virginia slaves left their masters during the American Revolution to take Dunmore and Clinton up on their offer of freedom to slaves who would be willing to fight with the British against the American revolutionaries. Pybus says this figure is way too high. Despite differences in their calculations, how can we tell from the overall gist of Frey's article "Between Slavery and Freedom" that Frey would accept Pybus figures for Virginia as more accurate than Jefferson's
One important factor that contributed to the Atlantic slave trade during the time of European colonialism was the high demand for labor in places like the Caribbean, where sugar was being harvested due to its high demand in Europe.