1. A computer-implemented method of performing sentiment analysis, comprising: performing a first sentiment analysis on microblogging data based on a method using an opinion lexicon; training a classifier using training data from the first sentiment analysis; identifying a new opinion term in the microblogging data, by performing statistical test, wherein the new opinion term is not in the opinion lexicon; identifying new microblogging data based on the new opinion term; and performing a second sentiment analysis on the new microblogging data using the classifier.