As we approach Emancipation Day 2026, reflections on the transatlantic slave trade demand more than surface-level commemoration — they demand a clear-eyed examination of the deeply commercial infrastructure that sustained the centuries-long system of human trafficking. This inquiry began for me, a scholar researching the evolution of global financial institutions from antiquity to the modern era during my doctoral studies at the University of Manchester, when I first encountered the hidden business records of the trade in enslaved people. Among these records, one document stands out as a singular and unflinching window into the day-to-day operations of the trade: the diary of Antera Duke.
Duke, a prominent Efik merchant prince and leader of what was then Duke Town (in present-day Nigeria), kept his daily journal between 1785 and 1788, written in the trade English commonly used along the West African coast. First published in a comprehensive scholarly edition by Oxford University Press in 2010, this diary is the only known surviving day-by-day account of the slave trade written by an African slave trader. What makes it so striking is its unemotional, strictly commercial tone: Duke logs customs duties (called “comey”) collected from European ship captains, records dinners hosted aboard British vessels from Liverpool, details credit disputes and their resolutions, and tracks consignments of enslaved people delivered downriver to waiting buyers. There is no moral hand-wringing, no indication of the horror of the trade being documented — it is, unapologetically, the journal of a businessman running a profitable enterprise.
Duke’s diary forces a critical, often overlooked question: before enslaved people were sold at auction in Richmond, Virginia, before they were forced to harvest sugar cane in Barbados, before they were packed onto overcrowded transatlantic crossing ships, who ran the upstream commercial business of capturing and selling enslaved people, and what were the terms of that trade? The historical record is uncomfortable on all sides, and it contradicts the common simplified narrative that Europeans directly captured most enslaved people themselves.
In reality, the harsh disease environment of coastal West Africa earned the region the nickname “the white man’s grave”: roughly half of all newly arrived European settlers and traders died within a year of landing, forcing Europeans to remain on their ships or in isolated coastal forts, relying entirely on local African actors to supply the enslaved people they purchased. The work of capturing, marching, and selling enslaved people at coastal trading points was controlled by West African states and established merchant networks: the Kingdom of Dahomey, which operated the key port of Ouidah under a royal customs monopoly; the Aro trading network of Igboland; and the canoe-house merchant firms of Bonny and Old Calabar, where Duke himself was a leading partner. Enslaved people were acquired through a range of violent systems — warfare, raids, judicial punishment, debt seizure, and kidnapping — before being sold directly to European buyers at coastal trading beaches, where the African supply network and European shipping industry converged.
This history cannot be softened, but it also cannot be reduced to a single simplistic narrative. The historical archive holds two concurrent truths that must both be acknowledged: many African rulers and merchants profited directly from running the supply side of the trade, but other African leaders recognized the catastrophic damage the trade was inflicting on their communities and spoke out against it centuries before abolition. As early as 1526, Afonso I, the Christian monarch of the Kingdom of Kongo, wrote a formal letter to the King of Portugal protesting that Portuguese-backed traders were seizing his people daily, writing that “our country is being completely depopulated” and begging the Portuguese crown to send priests and religious materials rather than more slave traders and trade goods. This letter survives in official archives to this day. The demand for enslaved people came from European powers across the Atlantic, and that demand transformed and industrialized violence across inland West Africa. Both facts are equally true, and neither negates the other.
Tracing the flow of money through the trade also reveals how interconnected the early modern global economy already was, built entirely on the exploitation of enslaved people. The price of an enslaved person was calculated in a negotiated “assortment” of goods, valued in standardized trade units like the trade ounce. Contrary to popular myth, these assortments were not made up of cheap trinkets. Economic historian David Richardson’s analysis of more than 90 English slaving voyages found that the highest-value category of goods traded was textiles, most notably handwoven Indian cottons from Gujarat and Bengal. Next came guns produced in Birmingham, with hundreds of thousands of firearms traded annually at the height of the trade. The bundle also included iron bars, distilled spirits like brandy and rum, and cowrie shells harvested in the Maldives and shipped by the ton to West Africa to use as small currency: abolitionist and formerly enslaved author Olaudah Equiano recorded that he himself was sold for 172 cowries. This means a weaver in Bengal, a gunsmith in Birmingham, a shell diver in the Maldives, and an enslaved laborer in the Caribbean were all part of a single interconnected global supply chain, even if they never knew one another existed. As demand for enslaved people outstripped supply through the 18th century, prices rose roughly five-fold along the West African coast, following standard commercial market dynamics.
Even the transatlantic slave ship itself functioned as a sophisticated financial instrument. A typical English slaving voyage was divided into 64 tradable shares, held not just by wealthy elite merchants, but also by small investors: local shopkeepers, clergymen, even widows who held a single 64th share as a long-term investment. By 1790, outfitting a single slaving voyage out of Bristol cost roughly £8,500, and the full round trip from Europe to Africa to the Americas and back took 12 to 18 months, with profits mostly returning to investors as bills of exchange drawn on London banks. The popular textbook narrative of a neat triangular trade of goods, enslaved people, and sugar is partially a myth; most returns from the voyage came in the form of financial paper, not physical cargo.
Voyages were fully insured, with premiums totaling roughly 10% of the total outbound cost. The Middle Passage crossing itself was priced at a 4.8% premium, with each enslaved person insured for £30 per head. Insurance policies explicitly excluded coverage for deaths from illness, suicide, or insurrection, unless losses exceeded 10% of the cargo’s total value — a quiet acknowledgment of the constant risk of both disease and rebellion on these voyages. Notably, economic historians who have reconstructed historical underwriting records find that slaving voyages were not unusually risky investments to insure; in fact, insuring a voyage run by the British East India Company cost more than insuring a slaving voyage.
When the British Parliament first passed regulation of the slave trade in 1788, it regulated the trade purely as a logistical and commercial enterprise. The Dolben’s Act set a legal limit on the number of enslaved people a ship could carry based on its tonnage: the Liverpool ship Brookes, which had previously carried 609 enslaved people in a single voyage, was now legally permitted to carry only 454, with each enslaved man allotted just six feet of length and 16 inches of width of space. The act even included incentive pay: captains received a £100 bonus and surgeons received a £50 bonus if mortality during the crossing fell below 2%.
Mortality was explicitly treated as a key performance indicator for the trade. Across the entire transatlantic trade, roughly one in every seven enslaved people died during the Middle Passage crossing. Abolitionists quickly exposed a second devastating mortality statistic that proponents of the trade could not refute: European crew members died at shocking rates too. When abolitionist Thomas Clarkson analyzed official crew muster rolls, he found that in a single year, 216 of 910 Bristol slave-trade sailors died — more deaths than the rest of Britain’s commercial shipping combined over two years. The trade, often hailed by proponents as a “nursery of seamen” for Britain, was in fact a deadly graveyard for the sailors who worked on the ships.
What kind of profits did the trade actually generate? Modern scholarship delivers a cold, clear answer: average profits for British slaving voyages landed between 8% and 10%, with one careful analysis by historian Roger Anstey finding an average return of 10.2%. While there was enormous variance across voyages, and some large firms earned far higher returns during boom years, the consensus average tells an important story: the slave trade delivered a normal commercial return, comparable to other ordinary shipping investments. The trade persisted for three centuries not because it was an extraordinary, once-in-a-generation bonanza, but because it was an ordinary, diversified, insurable, and socially respectable investment open even to a clergyman’s widow with a single share.
While investors in Europe earned steady, ordinary returns, Africa paid a catastrophic cost that no financial ledger ever recorded. One careful demographic estimate suggests that Africa’s total population in 1850 was half what it would have been without the transatlantic slave trade, and modern economic analysis still finds the long-term structural scars of this depopulation and exploitation in contemporary development data.
The trade was built on systematic record-keeping and ledgers, but it was also dismantled by activists who used the same tools of data and documentation to expose its horrors. Clarkson’s mortality tables from crew muster rolls, the widely circulated diagram of the overcrowded ship Brookes printed and distributed 7,000 times across Britain, Equiano’s bestselling memoir of his experience of enslavement and freedom: these formed the first data-driven human rights campaign in history, where numbers were marshaled to challenge the power of the pro-slave trade lobby. This work stands in that long tradition of using clear historical evidence to confront the legacy of the slave trade.
But Antera Duke’s diary leaves no room for comfortable moral certainties, and it should leave readers uneasy as well. Both European buyers and African sellers kept careful commercial ledgers of the trade in human lives. There is no easy way to cast all responsibility on “somebody else” when the historical record makes clear that actors on both sides of the coastal trading beach participated in and profited from the system. Every generation, as it confronts the legacy of slavery, has to decide for itself which side of that beach it stands on.
Tomorrow, Part 2 of this series will examine the auction room where enslaved people were sold in the Americas, and the financier who bankrolled the trade.
This article is written by Professor C. Justin Robinson, Pro Vice-Chancellor and Principal of The UWI Five Islands Campus.