How do I know that the KC score measures competition accurately? When I first started using the KC feature – I didn’t know for sure. But I’ve been using it since December of 2012. I’ve published literally hundreds of different articles (in different niches) around keywords with low to medium KC scores and I have a pretty good feel for the accuracy. More than 5 years of successfully ranking for low competition keywords has convinced me to completely trust the KC scores that are calculated within Long Tail Pro.
Long Tail Pro is a keyword research tool that helps you quickly find low competition keywords for your website. In particular, the tool is built for people doing SEO (search engine optimization) as opposed to people doing paid ads (Google Adwords PPC). I'm sure there are some advertisers that use the tool for paid ad keyword research, but the tool was built for SEO keyword research.