Sui, Tang, Qin, and Zhou fit that pattern. Can't forget the Jin, Liao, Xia, and Yuan. Also, another geographic factor I forgot to mention was the fact that mu

Sui, Tang, Qin, and Zhou fit that pattern. Can't forget the Jin, Liao, Xia, and Yuan. Also, another geographic factor I forgot to mention was the fact that much of China's land is just unsuitable for the kind of modern farming technology that was developed in the west. (Try running a harvesting combine over this: http://www.jacobsexposure.com/wp-content/uploads/2013/09/MJP_5596.jpg http://www.jacobsexposure.com/wp-content/uploads/2013/09/MJP... or, for another matter, this: http://i.imwx.com/web/multimedia/images/content/China_drought.jpg http://i.imwx.com/web/multimedia/images/content/China_drough... ) South China is too hilly and has too much water, meanwhile North China has never had enough water. The relatively poor rice/grain farming productivity in China was a pretty major obstacle to technological progress. Too much of the population had to rely on subsistence farming, and famine was a constant threat from time immemorial up until about the 1980s.