Keyword Diversity Trend of Consumer Generated Novels

Recent years, CGM (Consumer Generated Me- dia), such as YouTube and nicovideo.jp for movies, syosetu.com for novel stories, become very popular. A lot of contents are posted to CGM sites every day, and also a large number of users are enjoying posted contents. At present, some articles mentioned decreasing diversity of contents. Some posted new content may be similar with previous posted contents. The authors are afraid that decreasing diversity of contents causes less energetic cultural activity. In this paper, the authors proposed two quantitative metrics of contents diversity, and applied them to the contents in syosetu.com. They focused the keywords which are given to the novel by the novel author, and calculated entropy and similarity of keywords. As the results, they observed increase of similarity, and it shows decrease of diversity of contents.