Most of the workers are coming from places outside Yiwu, and their population has exceed the local ones. And most of local population are business owners and factory owners.

I haven't heard of any child labor involved, For Yiwu is rich and has very high level of education and not lacking of workers here.

I think what made Yiwu as a global wholesale place is most of its history. The first group of Father-Candy-Man came in 1600s.[1]

It has many many foreigners and a good culture around them, you'll love it when you come and visit it.

[1] http://www.yiwu-market-guide.com/yiwu-market-history.html