I don’t think that’s imported. It’s complicated by the hukou system, but all these people are Chinese, share the same culture (and to a great extent language).

In addition, these people made a calculus where staying in their ancestral homes meant certain poverty and moving to the city meant immediate increase in income as well as better prospects for the future. The drawback is/was poor working conditions, but I’m not sure they are worse than those back in their an ancestral homelands.

Those migrant workers in China are literally getting a better life through hard work or at least a better life for their children. They're not exploited, they're exploiting the money being offered them by the wealthier city people. Their work might not be very attractive to westerners, but neither was our ancestor's work, yet it still improved their and their descendants' lives.

So you're saying people born in poor farming communities are being taken advantage of by the massive creation of higher paying jobs in the cities?

Ok. But what about the formerly rural workers? Their standard of living has dramatically risen as well.