A reference which has these numbers: 11-15 million African slaves bought and brought to the Americas. Only 5-7 % of these ended up in U.S. This gives a range of between roughly 500,000 to 1,000,000 slaves whose African owners sold them to slave traders who brought them to the U.S.
I have seen statistical abstracts that put the number of African immigrants during the 300+ slave-trade years at about the same numbers. This includes indentured apprentices, etc. (so perhaps you might consider them as unfree). I can't seem to find on-line sources of immigrant data prior to the 1820's. Or perhaps my recollection is hazy. So unless I find other documentation, my statement should read that prior to the Civil War, "about half" were brought as slaves, about half came as immigrants.
Of course, since the Civil War, literally millions of Africans have emigrated to the U.S., none of whom were slaves.
Statistically (with rounding), it breaks down thusly:
pre Civil War: 1,000,000-2,000,000 African "immigrants"; 50% slave
post Civil War: 8,000,000-10,000,000 African immigrants; 0% slave
So, yes Virginia, the ratio of African slaves to African immigrants is quite low.
No reply needed, or expected.
btw, I reckon you agree with the rest of my post then.