This is a good point, though at the time of my comment it's already attracted several "that's racist" type responses. I think generally you might be getting at

This is a good point, though at the time of my comment it's already attracted several "that's racist" type responses. I think generally you might be getting at Simpson's Paradox[0] where an aggregated trend is in one direction when all the relevant subgroups are in a different direction, and it's just that the makeup and proportions of those subgroups has changed. My father in law is a guidance counselor in Florida. He told me about a school in the county that was ranked very poorly 10 years ago, but is now one of the top. I was curious how they did it, but it apparently had nothing to do with changes in curriculum, but the fact that somehow that area had become a destination for wealthy Chinese international students, and the student body had become dominated by them. [0] https://en.wikipedia.org/wiki/Simpson's_paradox https://en.wikipedia.org/wiki/Simpson's_paradox