Your numbers are off. 15 million people were taken onto the slave ships over 3 1/2 centuries. 11 million of them arrived in the Americas. 4 million died en route. Remember, slaves meant money, so the slave traders had the biggest reason of all to keep accurate counts.

And while we're on this, will you tell Arabs that they are responsible for the deaths of maybe 120 million (that's right!) Africans who died in the Sahara as part of overland slave coffles over 14 centuries? 18 million of them made it to the markets of Fez, Cairo and, yes, Mecca, over 14 centuries (and it's probably still happening under the law's radar). Not to mention that they were often the middlemen who sold Africans to Europeans. For more info, google John Azumah Adembillah and his book The Legacy of Arab Islam in Africa.