AdWords shows you logarithmic stuff... that search volume bar is nowhere near linear, plus the volume it represents is just as dynamically 'interpreted' as the graph in Trends. Meaning it's relative to the rest of the keywords on your list. Mind you Trends is linear, it just clips off stuff at the bottom ( mainly for commercial phrases ). The difference between keywords on the graph is logarithmic however. ... my advice is use as many tools as you can, and do cross-examinations. a single tool can be wrong... two tools can still be wrong, but 4 to 5 independent tools will give you an idea at least. Other issues include that Trends will show you the volumes for all queries made that included the set words, phrase. Using quotes will make it at least somewhere between phrase and exact match, but it's unlikely that you'd be able to get stats for a single, stand-alone phrase. So when more and more people are satisfied with the results their first, generic search shows them... ...let's say, 'blue widget' ...they are less and less likely go into refining searches, right ? 'blue widget mycity'
'blue widhet review' ...etc. Meaning exactly what you see: lower volumes showing in Trends and higher trtaffic volume coming from the top tier keywords. ( fewer times the phrase was used in searches... but more and more people coming from Google ) just one of the possibilities though. ...
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