Bryan, I may not have explained myself well. My point is it's not just population dynamics that's driving the epidemic of school shootings in the US. By Tim's account it seems to be almost exclusively a white problem, and by world standards, it's almost exclusively a US problem. Ergo, white Americans are unusual in the frequency with which they conduct mass shootings - especially in schools. (And yes, I know there are exceptions, but they are just that, exceptional - not in a good way. On the other hand, mass school shootings in the US are commonplace.)