More specifically, we compare five unsupervised keyphrase extraction algorithms on four corpora with varying domains and statistical characteristics. These algorithms represent the ma-jor directions in this research area, including TfIdf and four recently proposed systems, namely, TextRank <cite>(Mihalcea and Tarau, 2004)</cite> , SingleRank (Wan and Xiao, 2008) , ExpandRank (Wan and Xiao, 2008) , and a clustering-based approach (Liu et al., 2009b) .