The portion of the global population that experiences fall colors is somewhat high, but I never really thought about how little of the world’s land sees it. Northeast north america, half of Europe, and part of China. Warmer places don’t make trees go into winter mode and colder places don’t support deciduous trees as well. It can’t be too dry for them, either, which precludes much of the southern hemisphere. So it happens across the globe mostly in the same couple of months