Not very many, at any rate. But if they applied, it wouldn't really be slavery, would it? Just a crappy job, no talk of "reparations" for involuntary servitude. Kind of like the deal the Scots-Irish got during the 18th and 19th century, in exchange for their passage to the New World.
Of course, the Scots-Irish aren't asking for reparations either. Perhaps they realize that in the long run, they got a good deal by being able to come here, and they were grateful for it. That's what my grandparents told me, anyway.