From The New York Times:
Since 1990, according to immigration figures, more [Africans] have arrived voluntarily than the total who disembarked in chains before the United States outlawed international slave trafficking in 1807. More have been coming here annually – about 50,000 legal immigrants – than in any of the peak years of the middle passage across the Atlantic, and more have migrated here from Africa since 1990 than in nearly the entire preceding two centuries.