From 1526 to approximately 1870, slave ships from various countries loaded slaves from Africa and took them to somewhere in the Americas.
(Note, in this question, I use "America" and "Americas" to refer to either North or South America, or both.)
When I search for how many, almost always I either find a giant lump sum, or the number of slaves imported by British slave ships. So what I'm looking for now is non-British slave ships. How many African slaves were imported by Portugal, Spain, France, etc.?
Do these numbers exist? Surely logs must exist for these countries' ships just as they do for Britain's.
Current estimates are that about 12 to 12.8 million Africans were shipped across the Atlantic over a span of 400 years.
I'm just pointing this one out to illustrate that, presumably someone did tally up all the slaves from the individual nations' slave ships, or else the sales purchases at American ports. If the latter, then hopefully those purchases have a record of who sold them.
The same article also says
The major Atlantic slave trading nations, ordered by trade volume, were: the Portuguese, the British, the French, the Spanish, and the Dutch Empires.
But this sentence has no source, and it does not even give any numbers for the volume. Nor does it give a date range. Date range is important because I'm pretty sure Britain was the number 1 importer from roughly 1700 - 1830, but later was surpassed by Portugal. I gleaned this from another website, abolition.e2bn.org, saying
In the 1660s, the number of slaves taken from Africa in British ships averaged 6,700 per year. By the 1760s, Britain was the foremost European country engaged in the Slave Trade. Of the 80,000 Africans chained and shackled and transported across to the Americas each year, 42,000 were carried by British slave ships.
That's more along the lines of the info I'm searching for, except it only gives a number for Britain. I would really like to know how many slaves were transported by each European country.
Note: This question is only asking about slave trade from Africa to the Americas. I'm aware that slave trade also existed from Africa to Asia, that many new slaves were the result of births in America, and many other slaveries existed all over the world. For this question I am only interested in slaves loaded onto ships at Africa going to the Americas.