Sentiment classification has become a hot research topic in NLP community and various kinds of classification methods have been proposed, such as unsupervised learning methods (Turney, 2002), supervised learning methods (Pang et al., 2002), semi-supervised learning methods (Wan, 2009;Li et al., 2010), and cross-domain classification methods (Blitzer et al., 2007;Li and Zong, 2008;He et al., 2011).
imbalanced sentiment classification is relatively new and there are only a few studies in the literature.