I've come to Changle trying to solve a riddle: Why would hundreds of thousands of people leave this area, often risking their lives in the process, to move to America and live as illegal aliens, making minimum wage or worse, when Fujian province has never been, by any stretch, the poorest part of China? As part of Deng Xiaoping's reforms in the 1970s and '80s, several Fujianese cities, including Fuzhou, became special economic zones, where some free enterprise was tolerated. During the 1990s, when people were leaving Changle in epic numbers, the economy was experiencing double-digit growth.
Migration specialists have looked into this, and it turns out that it is not absolute poverty that drives people to leave one country for another. When everyone shares the same meager lifestyle, there is less of an inclination (and less means, presumably) to leave. Instead, economic migration in places like Changle is driven by "relative deprivation": income disparities and the experience of watching your neighbor do better than you. So, ironically, economic development sometimes causes people to leave.
The story ends well as brain drain turns to brain circulation. What interests me is the detail used to describe the migration network that would benefit Changle. My intention is to build something similar for Pittsburgh, but doing so for the entire mega-region also makes sense.