Derb, having served years ago as The New York Times West Africa bureau chief based in the Ivory Coast, I think I can answer your question.
In those days, when Felix Houphouet-Boigny was president and there were more French living in Cote D’Ivoire then there had been under colonialism, the country’s economy was dynamic and immigrants seeking jobs came from Benin, Burkina Faso (formerly Upper Volta), Sierra Leone and other neighboring nations.
There was one additional factor: Ivorian laws made it virtually impossible to fire an Ivorian. The result was that most people — myself included — preferred to hire foreigners. This was resented by the locals.
I don’t know, and do wonder, if today ,with the country suffering civil war and virtual collapse, the Ivory Coast remains such a magnet for foreign workers.