Slavery, by the Numbers

100 Amazing Facts About the Negro: Twenty-eight statistics every American should know this Black History Month.

Cotton harvest Thinkstock

1. In the history of the trans-Atlantic slave trade (1525-1866), 12.5 million Africans were shipped to the New World. Of them, 10.7 million survived the dreaded Middle Passage, disembarking in North America, the Caribbean and South America. Only about 388,000 were transported directly from Africa to North America, as David Eltis, David Richardson and their colleagues have definitively established in the Trans-Atlantic Slave Trade Database.

2. Children typically comprised 26 percent or more of a slave ship’s human cargo, David Eltis writes in his “Brief Overview of the Trans-Atlantic Slave Trade.” On average, the voyage took “just over two months,” and because of “filthy conditions,” “a range of epidemic pathogens” and “periodic breakouts of violent resistance,” “between 12 and 13 percent of those embarked did not survive the voyage.”

American-Style Slavery

3. The importation of slaves into the United States was banned by Congress (under Constitutional command) in 1808, yet by 1860, the nation’s black population had jumped from 400,000 to 4.4 million, of which 3.9 million were slaves. The primary reason was natural increase, a distinguishing feature of American-style slavery. Between 1790 and 1860, reports Ronald Bailey, author of “The Other Side of Slavery: Black Labor, Cotton, and Textile Industrialization in Great Britain and the United States,” in the spring 1994 issue of Agricultural History, the U.S. slave population increased between 25 percent and 33 percent per year—an average of 28.7 percent over the period. 

4. In the U.S., on average, a slave mother gave birth to between nine and 10 children, “twice as many in the West Indies,” according to the Gilder Institute of American History. Yet, in 1860, “less than 10 percent of the slave population was over 50 and only 3.5 percent was over 60.

5. Speaking of “natural increase,” in that same year, 1860, the venerable historian Ira Berlin writes in his classic text, Slaves Without Masters, “fully 40 percent of the Southern free Negro population were classified as mulattoes, while only one slave in ten had some white ancestry.” The obvious reason: Masters were more likely to free slaves who looked like—and, in many cases, descended from—them. And sometimes—not often enough—these slaves were able to earn enough money working on their own to purchase their freedom and that of their wife and children. The average African American today, according to Joanna Mountain at the genetics company 23andMe, “is 73.4 percent African, 24.1 percent European, and only 0.7 percent Native American” in their genetic makeup.

6. Largely as a result of natural increase, the United States went from being a country that accounted for 6 percent of slaves imported to the New World to one that in 1860 held more than 60 percent of the hemisphere’s slave population, according to Steven Mintz, author of “American Slavery in Comparative Perspective,” for the Gilder Lehrman Institute. (It’s worth noting that  Stanley Engerman, Richard Sutch and Gavin Wright put that number closer to 50 percent in their March 2003 report on “Slavery” (pdf) for the University of California Project on the Historical Statistics of the United States.)

The Second Middle Passage

7. The Middle Passage refers to the trans-Atlantic slave trade. A second Middle Passage followed within the U.S. between the end of the Revolutionary War and the start of the Civil War. In all, my colleague Walter Johnson estimates in his book Soul by Soul: Life Inside the Antebellum Slave Market, “approximately one million enslaved people were relocated from the upper South to the lower South … two thirds of these through … the domestic slave trade.” In other words, two and a half times more African Americans were directly affected by the second Middle Passage than the first one.

8. The reason was business—specifically, the cotton trade. Where it flourished, in the states of Alabama, Mississippi and Louisiana, the slave population increased by an average of 27.5 percent per decade, demanding that entire families be relocated from plantations in the East and Upper South. In turn, Steven Deyle points out in his 2005 book, Carry Me Back: The Domestic Slave Trade in American Life, “Southern slave prices more than tripled,” rising from $500 in New Orleans in 1800, to $1,800 by 1860 (the equivalent of $30,000 in 2005). Of the 3.2 million slaves working in the 15 slave states in 1850, 1.8 million worked in cotton.