This Economist article explains the nature of urban growth in China. It says:
"Migration from the countryside has helped expand the urban population by 500m—the biggest movement of humanity the planet has seen in such a short time... China has swapped its socialist dream for an American-style one of cars and sprawling suburbs. The number of cars has increased more than tenfold in the past decade, to 64m... The ill-defined ownership rights of farmers have encouraged the sprawl. Officials can expropriate rural land easily and at little cost. Doing so is far cheaper than redeveloping existing urban areas. Industrial land is heavily subsidised, so factories have remained in urban areas rather than move to cheaper sites on city outskirts."
Read the full article here.