Migration and its role in China

You can only feel sad when you watch the documentary
 'Last train home'.
It tells the story about migration in China and its human costs by following a migrant family for three years.

Life as a Chinese migrant is hard in every aspects!

I can't help thinking:

1. Would China still have experienced a growing economy without the migrants that work in factories for very low wages?

2. Would the middle class and new rich emerge in China without the very cheap labour force?

I think not.

But how many people recognize that the migrants indirectly play a big role, when it comes to China's increasing economic and political power in the world?