For a long time, the SEO world has revolved around the idea that KW volume prediction tools could only give relative levels of accuracy, i.e. term X is more popular than term Y. These tools have never been good at fulfilling their true claim - predicting search volume.

I set up a campaign to test the predictions of KW research tools like KeywordDiscovery, Overture, Wordtracker, MSN, etc. It won't be ready to give up the data until the end of November (perhaps even later), but in the meantime, I thought it would be valuable to ask and discuss the various KW tools.

Obviously, there are lots of tools that pull from these primary data sources, but I'm more interested in which you generally find to be most accurate in predicting actual search volume.

I just accidentally deleted my first post here at SEOmoz (while trying to edit it), but luckily, it was also one of my worst posts ever, so it almost feels like fate...