Smith grasped the most essential feature of feudal society in China at that time-long-term stagnation. China is the country with the longest stagnation time in world history. It has a vast land, hardworking people and convenient transportation. It has already reached the prosperity that the feudal system can achieve. It became a powerful country as early as the Han Dynasty, but it has made little progress since then. According to an American economist's estimation, from the Western Han Dynasty to 1952, the per capita income of China only increased by about 20%. It's like a precocious child, who grew faster than others in the early stage, but never grew up again. Some scholars call China an "ultra-stable society", which refers to this stagnation. This feature of China society is the key to understanding China's modern problems-the complexity of China's difficult modernization process and its stubborn conservative consciousness are all due to this long-term stagnation.