China’s great migration started with farmers boarding crowded trains in Sichuan, Henan, and Hubei - poor provinces in China’s interior. A day or two later, they arrived here, along the Pearl River Delta, just north of Hong Kong, and became factory workers. Nearly a quarter of a billion people made this journey over and over for the past two decades. It was the largest human migration the planet has known, and it was fueled by our desire to buy things and by the Chinese hunger to make a better life for their families.