This makes sense only if this measures the power of the "empire" rather than the power/GDP of the region. "China" made roughly 20-40% of the world total populat

This makes sense only if this measures the power of the "empire" rather than the power/GDP of the region. "China" made roughly 20-40% of the world total population [1]. If you include nearby regions not under their control, Japan, Korea, Vietnam and also include India; you are pretty much looking at the population of most of the world. This is still true even today. This region has the best geography to create massive populations. And massive amounts of people generally correlated with massive powers. The only exception to this was during the early periods of globalization that culminated in Colonialism. Empires do wither out but their populations do not mostly disappear; which gives "re-birth" to other empires. China-India were always the center of the world but the same couldn't be said for their empires. 1: https://en.wikipedia.org/wiki/Population_history_of_China https://en.wikipedia.org/wiki/Population_history_of_China