As we count down to Emancipation Day 2026, a long-overdue deep dive into the inner commercial mechanics of the transatlantic slave trade, drawn from archival records and modern scholarship, reveals unflinching truths about how this centuries-long system operated. My first encounter with the business side of slavery came during my doctoral research at the University of Manchester, where I studied the evolution of global financial institutions from ancient to modern times. The unusual stories I uncovered in that research demand to be shared, even as they challenge comfortable narratives about this dark chapter of human history.
One of the most remarkable surviving artifacts of the trade is the daily diary kept by Antera Duke, a prominent Efik merchant prince and leader of Duke Town (in what is now modern Nigeria) between 1785 and 1788. Written in the coastal trade English of the era, the diary was published in a scholarly edition by Oxford University Press in 2010. To date, it remains the only known day-to-day account of the slave trade written by a slave trader from any continent. Far from the dramatic, charged narratives one might expect, Duke’s diary reads exactly like what it is: a routine business journal. It details customs duties (called *comey*) collected from European ship captains, social dinners aboard Liverpool trading vessels, negotiations to resolve credit disputes, and records of consignments of enslaved captives delivered downriver to waiting ships. Its tone is uniformly flat, commercial, and unemotional— a quality that makes it all the more unsettling.
Duke’s diary forces a critical question that is rarely centered in popular conversations about slavery: Before enslaved people were auctioned in Richmond’s slave markets, before they were forced to work on Barbados’ sugar plantations, even before they were packed onto transatlantic crossing ships, who ran the on-the-ground business of enslavement in West Africa, and under what terms? The surviving archival records are uncomfortable from every angle, forcing a reckoning with truths that have long been sidelined.
A frequently misunderstood fact is that Europeans rarely captured enslaved people themselves: they simply could not. West Africa’s tropical disease environment killed roughly half of all newly arrived European visitors within their first year, earning the region the well-documented nickname “the white man’s grave.” Confined to their ships and isolated coastal forts, European traders could only wait to purchase captives that were already brought to the coast by African actors. The capture, overland marching, and wholesale trade of enslaved people was entirely controlled by regional African states and established merchant networks: the Kingdom of Dahomey, which ran the key port of Ouidah under a state-controlled customs system; the powerful Aro merchant network of Igboland; and the canoe-house trading firms of Bonny and Old Calabar, where Antera Duke was a leading partner. Enslaved people were obtained through war, raids, judicial punishment, debt seizure, and kidnapping, before being sold directly to European traders on the coast— where the African procurement business connected to the European shipping business.
There is no reason to soften these uncomfortable truths, because history demands honesty. Equally important, the archival record also preserves the other side of this story. As early as 1526, Afonso I, the Christian King of Kongo, wrote an official letter to the King of Portugal protesting that European-aligned merchants were seizing his people every day. “Our country is being completely depopulated,” he wrote, requesting that Portugal send priests and sacramental supplies rather than slave traders and trade goods. This letter is preserved in official archives to this day. The historical record holds two simultaneous truths that do not cancel each other out: African rulers and merchants who ran the supply side of the trade for profit, and African rulers who recognized the catastrophic harm of the trade and formally opposed it five centuries ago. The massive demand for enslaved labor that came from across the Atlantic turned inland violence into a large-scale, industrialized system— both facts must be acknowledged.
Tracing the flow of money through the trade reveals how interconnected the early modern global economy already was. Enslaved people were priced in negotiated “assortments” of trade goods, valued in standardized units of account like the trade ounce. Contrary to popular myth, these bundles were not filled with cheap trinkets. In a landmark survey of more than 90 English slaving voyages, historian David Richardson found that the largest category of goods by value was textiles, most notably handwoven Indian cottons from Gujarat and Bengal. Next were guns from Birmingham, with hundreds of thousands of firearms exported to West Africa each year at the peak of the trade. Other common goods included iron bars, distilled spirits, and cowrie shells harvested in the Maldives, shipped by the ton to the Slave Coast to be used as small currency. The famous abolitionist Olaudah Equiano recorded that he himself was sold for 172 cowrie shells. A weaver in Bengal, a gunsmith in Birmingham, a shell diver in the Maldives, and an enslaved field hand in the Grenadines were all connected, often without their knowledge, in a single global supply chain. Like any market, the price of captives responded to supply and demand: Richardson’s data shows that the price of an enslaved person on the West African coast rose roughly fivefold over the course of the 18th century, as growing demand outstripped existing supply.
Even the transatlantic slave ships themselves functioned as formal financial instruments. A typical English slaving voyage was divided into 64 tradeable shares, held not just by wealthy elite merchants but also by small investors: local shopkeepers, clergymen, and even widows who held one 64th share as a retirement investment. Outfitting a single slaving voyage out of Bristol cost roughly £8,500 by 1790. The full round trip from England to West Africa to the Americas and back took 12 to 18 months, and most profits were returned to investors as bills of exchange drawn on London banks. The popular simplified “triangular trade” model of goods, slaves, and sugar is partially a myth: most of the value from the return leg came in the form of paper financial instruments, not raw cargo. Voyages were fully insured, with total premiums equal to roughly 10% of outward costs. The Middle Passage crossing itself was priced at a 4.8% premium, with each enslaved person insured for £30 a head. Insurance policies explicitly excluded coverage for deaths from illness or suicide, and did not cover losses from insurrection unless the insurrection destroyed more than one-tenth of the cargo. What do these clauses reveal about how the trade’s architects viewed the people they traded? Modern economic historians who reconstructed these insurance underwriting records found a surprising fact: insuring a slaving voyage was not considered an unusually risky investment. It was actually less risky to insure a slaving voyage than a voyage of the British East India Company.
When the British Parliament first passed regulation of the slave trade in 1788, it regulated the trade for what it was: a logistical commercial enterprise. Dolben’s Act set strict limits on how many captives a ship could carry based on its tonnage. The Liverpool ship *Brookes*, which had once packed 609 enslaved people onto a single voyage, was now legally limited to just 454. Each captive man was allotted a space just 6 feet long and 16 inches wide to lie during the crossing. The act even included performance incentives: a £100 bonus for the captain and £50 for the ship’s surgeon if mortality during the crossing fell below 2%. Mortality was explicitly treated as a key performance indicator, with financial rewards for lower death rates. Across the entire history of the trade, roughly one out of every seven enslaved captives died during the Middle Passage. A damning fact that defenders of the trade could never refute is that crew mortality was just as high. Abolitionist Thomas Clarkson analyzed ship muster rolls and found that in a single year, 216 of 910 Bristol slave-trade sailors died on voyages— more deaths than the rest of Britain’s entire commercial shipping industry lost over two years. The trade, often called a “nursery of seamen” by its supporters, was in fact a mass grave for sailors as well as captives.
So what profits did the trade actually generate? Modern scholarship delivers a cold, clear answer. The best contemporary estimates put average profits for British slaving voyages at roughly 8 to 10%, with one careful analysis by historian Roger Anstey finding an average return of 10.2%. Returns varied wildly from voyage to voyage, and some historians argue that the largest trading firms earned far higher returns during boom years. But the consensus average tells a critical story: the trade generated normal, respectable commercial returns, comparable to other shipping investments of the era. It persisted for three centuries not because it was an extraordinary bonanza for investors, but because it was ordinary, diversified, insurable, socially acceptable, and open to small investors like a clergyman’s widow with a single share.
While European and African merchant investors earned steady returns, Africa paid a catastrophic price that no ledger could ever record. One careful demographic estimate suggests that by 1850, Africa’s total population was half what it would have been without the transatlantic slave trade, and modern economic analysis still finds the long-term scars of this demographic collapse in contemporary development data.
The slave trade was built and maintained through careful record-keeping and accounting, and it was ultimately dismantled the same way. Thomas Clarkson’s mortality tables from muster rolls, the widely distributed diagram of the *Brookes* printed seven thousand times to show how captives were packed, Olaudah Equiano’s bestselling memoir: these were the tools of the first data-driven human rights campaign in history, where numbers and records were marshaled against entrenched political and economic power. This series of reflections on Emancipation Day stands in that same tradition. But Antera Duke’s diary leaves no room for comfortable moral compartmentalization, and it should not for readers either. Both European buyers and African sellers kept careful ledgers. No actor in this story can be neatly separated into “good” and “bad” sides. The intersection of these two ledgers was the slave trading beach on the West African coast, and every generation since has had to examine its own relationship to that history, and decide which side of that beach it stands on.
*This op-ed is contributed by Professor C Justin Robinson, Pro Vice-Chancellor and Principal of The UWI Five Islands Campus. NOW Grenada is not responsible for the opinions, statements or media content presented by contributors.*
