what are the reasons behind this phenomenon?
The great reform in 1978 is a milestone in Chinese history, which starts a new era of the nation. From that moment, Chinese government spared no effort on reforming the economic system and tried hard to pull itself from a poor and closed situation. The road of modernization is blooming yet twisting. Especially since early 90s, the process of modernization, reforming and opening up, the market economy are moving in depth.
However, as Chinese government was eager to see the reforming result and the country was in desperate need of capital accumulation, the policy of "Letting part of the people become rich, then the rich helps the poor after" was the start of the phenomenon.
Because of the policy preference, some people get quite rich in the early 90s. As time went by, the unfairness of income distribution and gap between rich and poor got larger and larger. With the development step went further, the actual interests and welfares of some classs and groups didn't increase as anticipated, while, they have to bear the cost of reform and opening up.
What's more, the rich group formed some interest groups. People with higher incomes also posses more resources in cultural, political and economic fields. With stronger economic power, they prefer to seek cooperation with political and cultural elites, which in turn could better protect their interest, however, the poor don't have the power to protect themselves, this lead to a greater gap among poor and rich.
In addition, the welfare system and social system in China, which aims at building a fair society, are unsound and still have a lot space for improvement.
All these reasons lead to a gap between the rich and poor, both economically and politically, and the phenomenon of disadvantaged groups raises.