It's mostly socio-economic. It has more to do with social class than ethnic group or race. The more economically you are at the top the more you will be surrounded by the dominant social group whatever that is. In the Americas and Europe that's people who are white or of Caucasian descent. Let us say I go to the luxury mall. How many white women do you think will be there as opposed to any other ethnic minority? White women are literally everywhere. Not that those other women do not exist but their percentage at the top of the socio economic strata is even lower than the general population. Where I work for example there presently are no "Black" women. Always been white ones though.