I agree that a more precise indicator (like ethnicity) is probably more useful. I think becoming even more precise than this likely is even more useful, howeve

I agree that a more precise indicator (like ethnicity) is probably more useful. I think becoming even more precise than this likely is even more useful, however with precision comes added complexity/specificity as well. That said, your example about Native American income groups isn't the argument you likely think it is. That has been investigated pretty thoroughly and found to be nearly entirely based on shared tribal ownership of businesses like casinos or oil fields, which pay out to the entire tribe. Overall Native Americans in the US are at a socioeconomic disadvantage compared to non-NA populations, primarily because they are in largely undeveloped (from a business/economic perspective) areas of the country, which are not considered targets of development. They suffer from both ethnic disparities as well as the same disparities that generally affect rural vs urban populations.