Why is the population in the east of China larger than that in the west?

Most of the China Plain is located in the east, and the average annual precipitation in the east is greater than that in the west, so historically, the east is more suitable for agricultural production and can support more people. Since modern times, the developed commerce and trade and rapid economic growth in the eastern coastal areas have prompted the population of the western region to move further eastward. Two reasons have jointly caused the situation that the population in the east is larger than that in the west.