This is a disease that origionated in Europe which is a country that is predominantly caucasian. Through the generations it has spread throughout different continents, (mainly the UK and the US) but you would be hard pressed to find an african american, mexican, russian (just for examples) with CF. I believe there is one african american on this website and that is the ONLY one I have ever heard of. For example, there is no dobut some caucasian in her immediate family (mom or dad) and some in her extended family as well (whatever parent is not caucasian has grandparents or greatgrandparents who had to have some caucasian in them).
I hope this answers the question. You might be able to find some more specific statistics and details if you type in CF and UK into a search.
Julie