WHy does Nicole Richie label as black !!!?

I think the origins of this started many years ago when black people were labeled as black even if they just had a drop of black blood. Personally, my grandmother was white, Indian and black...but because she had a little black she was identified as black. Remember, Nicole was raised by Lionel Richie who grew up in the South and probably handed down his own beliefs regarding identity. Nicole is black, but she is of mixed heritage. It is her choice how to self identify.