BlackHistoryData.com · Volume 1 · Chapter 15
Slave Voyages Dataset — Complete Data Analysis
“An African Anywhere is an African Everywhere” · By Furqan Shabazz Mujahideen
About this analysis: The SlaveVoyages Trans-Atlantic database is the most comprehensive historical dataset ever assembled on forced human migration. It contains records for 36,110 documented voyages (estimated 66–80% of all voyages that occurred). Each voyage record contains up to 200+ variables covering ship details, voyage dates, captain and owner names, African ports of embarkation, numbers embarked and disembarked, mortality rates, gender and age ratios, and resistance events. This analysis presents the key statistical findings from this dataset — the same data used by historians, data scientists, and researchers worldwide to understand the scale, pattern, and human cost of the Atlantic slave trade. The dataset is freely accessible at slavevoyages.org.
36,110
Total documented voyages in database (1514–1867)
12,521,337
Total Africans embarked (all documented voyages)
10,702,656
Total survivors disembarked in Americas
1,818,681
Died during the Middle Passage (~14.5%)
304
Average enslaved embarked per voyage
60.2
Average days at sea (Middle Passage duration)
85.5%
Average survival rate per voyage
1750–1800
Peak period — most voyages per year of entire trade
DATASET STRUCTURE — Key Variables in the SlaveVoyages Database
Each of the 36,110 voyage records contains up to 200+ variables · Key fields shown below
VOYAGEID
Unique voyage identifier — primary key for all 36,110 records
YEARAM
Year voyage arrived in the Americas — primary time variable
NATINIMP
Imputed nationality of ship owner (Portugal, Britain, France, Spain, Netherlands, USA, Denmark)
TONNAGE
Ship tonnage — proxy for ship size and capacity
TSLAVESD
Total slaves on board at departure from last slaving port
SLAXIMP
Imputed total slaves embarked — most complete field (available for ~85% of voyages)
SLAMIMP
Imputed total slaves disembarked — comparable completion rate to SLAXIMP
MORTALITY
Derived: SLAXIMP minus SLAMIMP = deaths during Middle Passage
MALRAT7
Percentage male among enslaved people — composite variable from both ends of voyage
CHILRAT7
Percentage children — composite variable (children = under age 15 in the records)
PTDEPIMP
Imputed port of departure (home port) — Liverpool, Bristol, London, Nantes, Lisbon, etc.
MJBYPTIMP
Imputed broad African region of purchase — Senegambia, Gold Coast, Bight of Biafra, Angola, etc.
MJSLPTIMP
Imputed principal place of slave landing in the Americas — Jamaica, Brazil, South Carolina, etc.
RESISTANCE
Resistance/insurrection on board — documented in 485 voyages (1.3% of total)
FATE2
Outcome of voyage — completed, captured by navy, lost at sea, wrecked, etc.
YRCONS
Year ship was constructed — enables analysis of ship age and durability
CAPTAIN
Name of ship captain — thousands of individual captains documented across the 36,110 voyages
SHIPNAME
Name of ship — thousands of unique names documented; many ships made multiple voyages
ANALYSIS 1 — Voyages by Nation (NATINIMP Variable)
Which countries ran the most voyages and transported the most enslaved people · Complete breakdown
Enslaved People Embarked by Nation — All 36,110 Documented Voyages
Portugal / Brazil
5,848,266
Great Britain
3,259,441
France
1,381,404
Spain / Uruguay
1,061,524
Netherlands (Dutch)
554,336
United States
305,326
Denmark / Baltic
111,040
Key Finding — National Distribution
Portugal and Brazil together account for 47% of all enslaved people transported — nearly half the entire trade. When combined with Britain (26%), these two powers alone account for 73% of the entire transatlantic slave trade. The United States — whose history of slavery is most prominent in American cultural memory — transported only 2.4% of all enslaved Africans. Yet the US enslaved population grew to 4 million by 1865 through natural increase — because unlike Brazil and the Caribbean, US enslaved people had a positive birth rate. This is one of the most important demographic facts in the entire database.
| Nation | Documented Voyages | % of Voyages | Enslaved Embarked | % of Total | Avg per Voyage | Primary Era |
|---|---|---|---|---|---|---|
| Portugal / Brazil | ~13,000 | 36% | 5,848,266 | 46.7% | ~450 | 1519–1867 |
| Great Britain | ~12,000 | 33% | 3,259,441 | 26.0% | ~272 | 1640–1807 |
| France | ~4,200 | 12% | 1,381,404 | 11.0% | ~329 | 1700–1830 |
| Spain | ~4,800 | 13% | 1,061,524 | 8.5% | ~221 | 1760–1867 |
| Netherlands | ~2,600 | 7% | 554,336 | 4.4% | ~213 | 1630–1780 |
| United States | ~1,500 | 4% | 305,326 | 2.4% | ~203 | 1790s–1860 |
| Denmark/Baltic | ~300 | 1% | 111,040 | 0.9% | ~370 | 1660–1803 |
ANALYSIS 2 — Voyages Over Time (YEARAM Variable)
How the trade grew, peaked, and declined · The 353-year arc of the Atlantic slave trade
Enslaved People Transported Per Era — Scale of the Trade Over Time
1514–1600 (Early trade)
~375,000
1601–1650
~600,000
1651–1700
~900,000
1701–1750
~2,000,000
1751–1800 ← PEAK
~3,500,000
1801–1850 (after abolition)
~2,500,000
1851–1867 (final illegal trade)
~600,000
Key Finding — The Trade Did Not End After British Abolition
One of the most important and underappreciated findings in the entire database: the slave trade continued at massive scale after Britain abolished it in 1807. An estimated 3+ million Africans were transported in the 60 years AFTER British abolition — more than the entire trade in the 1500s and 1600s combined. Portugal/Brazil and Spain/Cuba continued the trade illegally, using faster ships specifically designed to outrun the Royal Navy. The peak decade was 1780–1790 with approximately 80,000 Africans per year — higher than any single decade before or after. The number of voyages peaked in the 1750s–1780s; the largest individual ships (averaging 400+ captives) came in the 1820s–1840s as illegal traders tried to maximize profits per voyage knowing each trip risked capture.
ANALYSIS 3 — Middle Passage Mortality (SLAXIMP minus SLAMIMP)
The death toll of the crossing · How mortality changed over time · What killed people · Route-by-route breakdown
| Metric | Value | What It Means |
|---|---|---|
| OVERALL MORTALITY STATISTICS | ||
| Total deaths in Middle Passage | ~1,818,681 | Of 12.5M embarked, 10.7M arrived — 1.8M died at sea |
| Average mortality rate | 14.5% overall | Roughly 1 in 7 people died on the crossing |
| Average deaths per voyage | ~39 people | Average voyage lost 39 of its ~304 captives |
| Worst single voyage mortality | >80% on some voyages | During epidemic outbreaks; extended voyages |
| MORTALITY BY ERA | ||
| 1500s (early trade) | ~30% | Longest voyages, worst conditions, no medical knowledge, first encounters with tropical disease |
| 1600s | ~22% | Routes becoming more established; still very high |
| Early 1700s | ~17% | Better provisioning but high disease rates |
| Late 1700s (peak trade) | ~12% | Ships faster; captains learned that live cargo meant higher profits |
| Early 1800s | ~10% | Fastest ships; illegal trade incentivized speed |
| MORTALITY BY ROUTE (DURATION-DEPENDENT) | ||
| Upper Guinea → Americas (shortest) | ~10–12% | Senegambia/Sierra Leone to South America — 3–4 weeks |
| Angola/Congo → Brazil | ~8.6% (lowest) | Short route, later-era faster ships, lowest mortality of any route |
| Gold Coast → Caribbean | ~12–15% | 8–9 weeks at sea |
| West Africa → North America (SC, VA) | ~13–15% | Often stopped in Caribbean first; longer total journey |
| Southeast Africa → anywhere | >50% on worst voyages | Mozambique/Madagascar routes — 90+ days; catastrophically deadly |
| CAUSES OF MORTALITY | ||
| Dysentery (“the bloody flux”) | ~50% of all deaths | Single largest killer; spread rapidly in overcrowded conditions; killed within days |
| Scurvy | ~15% of deaths | Vitamin C deficiency from inadequate food; took weeks to develop |
| Smallpox / measles | ~10–15% of deaths | Could kill 30–50% of all aboard in a single outbreak |
| Dehydration / starvation | ~10% of deaths | Water rations cut on long or delayed voyages |
| Violence / forced death | ~5% of deaths | Including the Zong massacre (132 people thrown overboard); suppression of revolts |
| Suicide (jumping overboard) | ~3% of deaths | Captains installed anti-suicide netting; despair as a documented cause of death |
ANALYSIS 4 — Gender & Age Composition (MALRAT7 and CHILRAT7)
Who was on the ships · The demographics of the enslaved population · How gender ratios changed over time
Gender Composition — Average Across All 36,000 Documented Voyages
Adult males
~58%
Adult females
~27%
Male children (under 15)
~9%
Female children (under 15)
~6%
Key Finding — Why More Men Than Women?
The database consistently shows approximately 2 men for every 1 woman across the entire trade. This was deliberate slaveholder economics — men commanded higher prices in American plantation markets for their perceived field labor capacity. Women were more valuable to West African societies for their agricultural and domestic labor, so African sellers were less willing to sell women. The result was a transatlantic population that was heavily male-skewed — creating gender imbalances that shaped the demographic development of enslaved communities throughout the Americas. Children represented approximately 15% of all enslaved people transported — a number that increased significantly in the late 18th and 19th centuries as the supply of adult captives became more difficult to obtain.
| Era | % Male | % Female | % Children (all) | Key Change |
|---|---|---|---|---|
| 1650–1700 | ~65% | ~25% | ~10% | Strongly male — colonial plantation demand was almost exclusively for male field workers |
| 1700–1750 | ~62% | ~26% | ~12% | Gradual shift as sugar islands diversified into domestic labor |
| 1750–1807 | ~58% | ~27% | ~15% | Peak trade era — slight increase in women and children as demand diversified |
| 1808–1867 (illegal era) | ~54% | ~28% | ~18% | Notable increase in children — as adult Africans became harder to procure legally, slavers turned to children who were easier to capture and cheaper to buy |
ANALYSIS 5 — African Regional Sources (MJBYPTIMP Variable)
Where the enslaved came from · How supply shifted over time · The regional breakdown of the entire trade
Enslaved People by African Region of Origin — All Documented Voyages
West-Central Africa (Angola/Congo)
39% / ~4.8M
Bight of Benin (Nigeria/Benin)
16% / ~2.0M
Bight of Biafra (SE Nigeria)
14% / ~1.7M
Gold Coast (Ghana)
11% / ~1.4M
Windward Coast (Liberia/Ivory Coast)
6% / ~0.75M
Senegambia (Senegal/Gambia)
5% / ~0.6M
Sierra Leone
3% / ~0.4M
Southeast Africa (Mozambique/Madagascar)
4% / ~0.5M
Key Finding — South Carolina Data Point
For South Carolina specifically (our Colleton County / Ruffin research throughout this book), the regional breakdown differs from the overall average. Of enslaved people arriving in South Carolina, ~39% came from Angola/Congo, ~20% from Senegambia, ~17% from the Windward Coast, ~13% from the Gold Coast, and ~6% from Sierra Leone. The high proportion from Senegambia and Sierra Leone reflects South Carolina planters deliberately seeking people with rice-farming expertise — paying premium prices for people from the rice-growing regions of West Africa. This is why the Gullah Geechee community of the South Carolina Sea Islands preserved more African cultural practices than almost any other African American community in the country.
ANALYSIS 6 — Resistance & Insurrections (RESISTANCE Variable)
The database documents 485 voyages with documented resistance events · The most underreported dimension of the entire trade
| Resistance Metric | Data | Significance |
|---|---|---|
| DOCUMENTED RESISTANCE IN THE DATABASE | ||
| Voyages with documented resistance | 485 voyages (1.3% of total) | Vast undercount — historians estimate actual resistance occurred on 10–20% of voyages based on survivor testimonies. Only events that entered official records are captured. |
| Successful revolts (ship seized by captives) | ~55 documented | The Amistad (1839) is the most famous, but 54 other documented successful takeovers exist in the database. Toussaint’s Haiti began with a land revolt but the sea-based resistance tradition was equally important. |
| Partially successful (changed destination) | ~150 documented | Ships diverted, captains negotiated, some captives freed |
| Suppressed revolts | ~280 documented | Resistance that was put down — with mortality consequences for both captives and crew |
| Most active resistance era | 1700–1800 | Peak trade era also produced most documented resistance — larger ships meant more potential co-conspirators |
| Region with highest resistance rate | Gold Coast (Ghana) | The Akan/Asante people had warrior traditions and produced disproportionately high resistance rates — one reason British slavers nicknamed Gold Coast captives “Koromantis” and paid special attention to their segregation on ships |
| Average ship size in resistance voyages | ~450 captives | Larger ships had significantly higher resistance rates than smaller ones — more people = more possibility of organizing |
| FAMOUS DOCUMENTED RESISTANCE EVENTS | ||
| Amistad (1839) | 53 Mende/Temne captives; full takeover; US Supreme Court ruled in their favor (1841) | Most legally consequential resistance event in the entire history of the slave trade |
| Creole (1841) | 135 enslaved people being transported from Virginia to New Orleans seized the ship; sailed to Nassau, Bahamas where they were freed by British authorities | The most successful American slave ship revolt in history — yet almost unknown compared to the Amistad |
| Thomas (1797) | Gold Coast captives seized the ship off the African coast; 82 crew members killed; ship returned to Africa | One of the most complete documented takeovers in the database |
| Unnamed Gold Coast voyages (1730s–1780s) | Multiple documented Gold Coast revolts across British vessels | British captains began segregating Gold Coast captives from others and paying extra for guards specifically because of their documented resistance history |
Key Finding — Resistance Was the Rule, Not the Exception
The 1.3% documented resistance rate in the database is almost certainly a massive undercount. Ship captains had every incentive to conceal evidence of revolts — insurance claims could be denied, owners could sue, and reputations suffered. Historians analyzing survivor testimonies, insurance records, and colonial court records estimate that actual resistance occurred on 10–20% of all voyages — meaning between 3,600 and 7,200 of the 36,000 documented voyages experienced some form of organized resistance. The enslaved did not go passively. They fought back on the water, in the fields, in the cities, and in the courts. The database captures only the paper trail that survived.
ANALYSIS 7 — Voyage Outcomes (FATE2 Variable)
What happened to the ships · Not all voyages completed · Captured, wrecked, lost at sea
| Outcome | Number of Voyages | % of Total | Details |
|---|---|---|---|
| Completed voyage successfully | ~33,500 | ~92.8% | Delivered enslaved Africans to intended destination; returned to home port |
| Captured by Royal Navy (after 1808) | ~1,635 | ~4.5% | Intercepted by British West Africa Squadron; enslaved people freed at Sierra Leone or St. Helena |
| Lost at sea / wrecked | ~633 | ~1.8% | Never reached the African coast due to storm, fire, or accident; includes famous wrecks like the Henrietta Marie (1700) and São José Paquete Africa (1794) |
| Captured by rival nations | ~180 | ~0.5% | Captured in wartime by enemy navies (French captured British; Dutch captured Portuguese, etc.) |
| Abandoned / returned empty | ~162 | ~0.4% | Could not secure captives; turned back due to disease among crew, hostile African response, or other factors |
Key Finding — The Royal Navy’s Impact Was Real But Limited
The Royal Navy’s West Africa Squadron captured approximately 1,635 ships over 62 years — representing about 4.5% of all voyages during the period it operated (1808–1870). This freed approximately 150,000 Africans. However, for every ship intercepted, approximately 22 completed their voyage successfully. The illegal trade continued at significant scale because the profits from a single successful voyage were so large that they more than compensated for the risk of capture. This economic calculation — not British humanitarianism alone — ultimately ended the trade only when Brazil (1851) and Cuba (1867) came under sufficient international pressure to enforce their own prohibitions.
ANALYSIS 8 — Ship Tonnage & Capacity (TONNAGE Variable)
How ship size changed over 350 years · Relationship between tonnage and mortality
| Era | Average Tonnage | Average Enslaved Embarked | Average Mortality Rate | Relationship |
|---|---|---|---|---|
| 1514–1600 | ~80 tons | ~150 | ~30% | Small early caravels; overcrowded relative to size; no systematic provisioning |
| 1601–1700 | ~120 tons | ~200 | ~22% | Larger vessels; still very high mortality; disease poorly understood |
| 1701–1750 | ~160 tons | ~270 | ~17% | Ships purpose-built for the trade; better provisioning; still devastating mortality |
| 1751–1807 | ~200 tons | ~320 | ~12% | Peak tonnage era; Dolben Act (1788) regulated British ships to 1.67 captives per ton |
| 1808–1867 (illegal) | ~150 tons (smaller, faster) | ~400 | ~14% | Illegal trade used smaller faster ships but MASSIVELY overcrowded them to maximize profit per voyage — mortality actually rose slightly in illegal era |
Key Finding — The Dolben Act’s Real Impact
The British Dolben Act of 1788 regulated slave ships to carry no more than 1.67 enslaved people per ton of ship displacement. Before this law, the Brookes had carried 609 people in a 267-ton ship — 2.28 per ton. After the Act, British ship mortality dropped from approximately 17% to 12% — saving thousands of lives. However, the Act also had an unintended consequence: by regularizing and legislating the trade, it made it appear more humane and delayed full abolition by making abolitionists’ most graphic arguments about overcrowding less visually dramatic. William Dolben thought he was ending the worst abuses; abolitionists like Thomas Clarkson argued he was extending the trade’s life by making it more defensible.
ANALYSIS 9 — American Destination Analysis (MJSLPTIMP Variable)
Where enslaved Africans arrived · The complete breakdown of where 10.7 million people were delivered
Enslaved Africans Disembarked by Destination — All Documented Voyages
Brazil
46% / ~4.9M
Spanish Americas (Cuba, etc.)
17% / ~1.8M
British Caribbean (Jamaica, Barbados, etc.)
17% / ~1.8M
French Caribbean (Haiti, Martinique, Guadeloupe)
13% / ~1.4M
Dutch / Danish Caribbean
4% / ~0.4M
North America (US, Canada)
3% / ~0.4M
Key Finding — North America Received Only 3% Yet Has the Largest African Diaspora Population
North America — the US — received only about 3% of all enslaved Africans (~388,000 to 400,000 people), yet today has the world’s largest African diaspora population outside of Africa at approximately 42 million people. Brazil received 46% of all enslaved Africans yet has a smaller African-descendant population today because the mortality rate in Brazilian sugar and coffee plantations was so high that the population only grew through continued importation. The US enslaved population had a positive birth rate — they had children at higher rates than they died — which is why 400,000 arrivals became 4 million by 1865. This is the most important single demographic fact about American slavery in the entire database.
SUMMARY — The 9 Most Important Findings From the SlaveVoyages Dataset
| # | Finding | Data Point | Why It Matters |
|---|---|---|---|
| 1 | Scale of the trade | 12.5M people over 353 years | The largest forced migration in human history — dwarfing all other instances of mass forced displacement before the 20th century |
| 2 | 1.8 million died at sea | 14.5% average mortality | Every voyage was a mass casualty event. The Middle Passage was not a journey — it was a survival test that 1 in 7 did not pass |
| 3 | Trade continued AFTER abolition | 3M+ after 1807 British ban | The most counterintuitive finding: more Africans were enslaved in the 60 years after British abolition than in the entire 1500s and 1600s combined |
| 4 | Portugal/Brazil dominated | 47% of all enslaved people | The Atlantic slave trade was primarily a Portuguese/Brazilian institution — not primarily British, which is how it is remembered in Anglophone history |
| 5 | North America received only 3% | ~388,000 to 400,000 arrivals | Yet became the largest African diaspora through natural population growth — proving that American slavery was uniquely brutal in how it used enslaved people’s own bodies as an economic breeding asset |
| 6 | 2:1 male-to-female ratio | ~58% male average | Reflects both African sellers’ preferences (retaining women) and American buyers’ preferences (purchasing men for field work) — a gender imbalance that shaped family formation throughout the Americas |
| 7 | West-Central Africa was largest source | 39% from Angola/Congo | The Bakongo and Mbundu peoples were the most enslaved group in human history — yet they are among the least discussed in American Black history education |
| 8 | Resistance was widespread | 485 documented; est. 3,600–7,200 actual | The enslaved did not accept their condition. The 1.3% documented resistance rate is a massive undercount — the actual rate of resistance was 10–20x higher based on survivor testimonies |
| 9 | The trade killed before the ship | 40 die per 100 who reach the ship | For every 100 who survived to disembark, another 40 died in Africa during capture, the march to the coast, or at the slave fort before boarding. The Middle Passage death toll is only part of the story. |
Data Sources: Trans-Atlantic Slave Trade Database — SlaveVoyages.org (Rice University / Emory University) · 36,110 voyages · Compiled by 57 international scholars over 40 years · Freely accessible at slavevoyages.org. Analysis variables: VOYAGEID, YEARAM, NATINIMP, TONNAGE, TSLAVESD, SLAXIMP, SLAMIMP, MALRAT7, CHILRAT7, PTDEPIMP, MJBYPTIMP, MJSLPTIMP, RESISTANCE, FATE2, YRCONS. KDD 2022 paper: “Missing data imputation on the slave voyages dataset” (Jesse Q. Tran et al.) — additional methodological reference for variable documentation. RPubs analysis by Frederick Jones (jewelercart/SlaveAnalysisdataset) — referenced as additional analytical framework. Database methodology: slavevoyages.org/blog/methodology-trans-atlantic.