Shouldn't he be looking at empire level data e.g. the growth of the US economy over the past 100 years, the British Empire in the 1800s, or the Roman Empire at

Shouldn't he be looking at empire level data e.g. the growth of the US economy over the past 100 years, the British Empire in the 1800s, or the Roman Empire at its height. No-one is saying Singapore or Cambodia is going to be the next world super power so how relevant is it to compare their 5 year growth spurts to what China is undergoing?