If it's trivial, why are results so variable on different ethnicity websites? And what happens when the definition of "white" changes in 30 years to unambiguous

If it's trivial, why are results so variable on different ethnicity websites? And what happens when the definition of "white" changes in 30 years to unambiguously include Latinos? (Hint : what you want is a classifier on ethnicity, and those aren't trivial either)