gmoney, I asked WebCEO the same question. They said they have a different approach to WordTracker and use data
accumulated over the last 6 months to calculate approximate number of daily searches for specific keywords. Search queries are sourced from:
A broader range of sources than WordTracker, but who can say if it's anymore representative?
Apparently new words are added to their database every day. Filtering is used to prevent the database being skewed with uncommon words that have been searched on in a particular search engine several times over a short period. However if such terms are normally searched for on in different search engines, they do get included, but some sort of special algorithm is applied.
Maybe this excludes some of the oddball results you can see in WordTracker? I only briefly trialed WebCEO so can't say either way.
Apparently world daily search figures are generated by applying a changing multiplier to get to the world daily searches number. So I guess that's similar to WordTracker's approach.
A big question I have about these tools is just how representative their sample data is of most search engine users.
I suspect most users of Meta search engines are comparatively unsophisticated web users. If that's the case, then simply extrapolating this sample set to predit total daily searches across all searche engines is flawed to some extent. Also WordTracker results are very American centric due to the Meta engines used. Possibly WebCEO's wider range of Meta search engines provides a more global or at least European perspective?
What do others think?