Google Keyword Tool
Google Keyword Tool is one of the most popular phrase research tools in the SEO community and many rely on it to understand traffic volumes behind phrases as well as level of competition for individual phrases.
- RELATED ARTICLE: http://dejanseo.com.au/introducing-phrase-potential-calculator/
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Greg Finn reports  the change in the way term competition is displayed. Little “PageRank” style green bar has been replaced by “Low” (under .33), “Medium” (.33-.66) and “High” (over .66).
 Finn, G. – Google Tweaks Competition Rank In AdWords Keyword Tool To “Low,” “Medium” or “High” Retrieved from: http://searchengineland.com/google-tweaks-competition-rank-in-adwords-keyword-tool-98510 on 27/10/2011