According to the Migration Policy Institute:
This six-minute video from AJ+ describes the push factors that influenced people in China to emigrate to the United States in four different waves. Chinese immigrants first came to the United States in the mid-19th century and continue to arrive well into the 21st century. While each family’s story is unique, the narrator explains that over time that Chinese people have left China for different reasons in different times including searching for economic opportunity, hopes a better life for their children, fleeing the impact of war, political persecution, and more recently in search of clean air and water.