I was trying to answer another question I had when I came across the Trans-Atlantic Slave Trade Database. According to one website, the Trans-Atlantic Slave Trade Database is "[t]he most comprehensive analysis of shipping records over the course of the slave trade." Further, of the database, that website says, "12.5 million Africans were shipped to the New World. 10.7 million survived the dreaded Middle Passage". I find similar numbers mentioned in places like PBS, Wikipedia, on Slave Voyages blog, and elsewhere. The online database, however, counts significantly fewer:

Summary Statistics of the Trans-Atlantic Slave Trade Database

And this includes ALL of the known slaves, not just the ones who disembarked in the Americas. The numbers for those disembarked in the Americas was again, significantly less:

Summary Statistics of the Trans-Atlantic Slave Trade Database regarding slaves who disembarked in the Americas

As a side note, I am wondering what the reason for the discrepancy in numbers is. Now, I know that many of the ships in the database lack information regarding the number of slaves onboard, so is this "12 million captured, 10 million arrived" figure adjusted for these ships that are of unknown capacity? Is the data adjusted for other known gaps in knowledge?

Specifically, has anyone investigated the completeness of the database, and if so, what known gaps exist in the data? For example, is it known that some records are missing. Such as, are port records missing for major slave ports for known periods of time. Or, for earlier years (laws mandated registry of slave ships in latter years), is it known approximately how many slavers sailed without ever registering; i.e. was this common or uncommon? Etc. Given that it appears that the numbers have been adjusted upwards, it suggests that some gaps are known.

I have been all over the the Slave Voyages website and I cannot find anything that answers the question. Google yields no results either.

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    Navigating that website takes some care. Same website, different page has the 12.5 Million figure.
    – justCal
    Commented Feb 19, 2023 at 21:34
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    @justCal That does help a little. That page is estimates, which suggests there are known gaps in the data coverage. Commented Feb 19, 2023 at 22:49
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    The other page you linked mentions the "imputed results are calculated by an algorithm" so also estimates. This page also only references a part of the database--only 34K voyages for some reason.
    – justCal
    Commented Feb 19, 2023 at 22:53
  • Ahhh, so the IMP by the figure stands for "imputed". I was wondering what it meant. Commented Feb 20, 2023 at 18:21
  • It would be more useful if you converted the images to text.
    – sds
    Commented Feb 21, 2023 at 18:00


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