The population shift from china occurred during the years of the song dynasty.

The answer is Northern Song. The population of China doubled in size during the 10th and 11th centuries. This growth was made possible by expanded rice cultivation in central and southern Song. The Northern Song census recorded a population of roughly 50 million. However, it is estimated that the Northern Song had a population of some 100 million people, and 200 million by the time of the Ming dynasty.

Blue ridge is the correct answer.