You've omitted the biggest killer of all the slave trades: the trans-Sahara slave trade that began in the seventh century in the wake of the Arab conquest of North Africa and which might still be going on under the law's radar. That slave trade killed about 120 million over the course of about fourteen centuries. And those Africans who were sold in Fez, Tripoli, Cairo and, yes, Mecca as well--where are their descendants today? Or are there any, as most of the men sold there were castrated?

Google John Azumah Adembillah's book, The Legacy of Arab Islam in Africa. That book will tell you plenty about this item. Also, google the Zanj uprising. That will tell you what happened when the Arabs tried plantation agriculture with African slave labor, at least for a while. After acquainting yourself with these atrocities, you might want to revise your opinion.