Hypergamy

Feminists are concerned that some Chinese women in their late 20s who are doing well in their careers but are labeled “leftover women” for not having married yet, may be their own worst enemies. 

While they may earn as much as their male counterparts they may still adhere to traditional beliefs that decree a man must earn more than his wife, and men generally share that belief. Either way, this attitude may limit their pool of potential mates.

http://rendezvous.blogs.nytimes.com/2013/04/23/how-chinas-leftover-women-are-to-blame/