China was a majority agrarian country a generation ago. Only 1 in 5 Chinese lived in urban areas in 1980, whereas today about 60% of them live in urban areas. Upward mobility has been the hallmark of this process in the country, with nearly 400 million of Chinese people joining the rank of the middle class during this time period. Use an economic theory to describe this exceptional economic transformation, making sure to outline the process in a detailed fashion.