section 2literature review
existing research mainly make concrete analysis and statistics about empty nesters, who are vulnerable grupes of society, by figures obtained from questionnairres and site visitings. The content are mostly about the real life of empty nesters: the condition of their material life, the extent of thier being taking care of, their relationship with descendents and how they are treated by them. And there are also some related research concerned about their feelings, like whether they feel helpless inside.