How accurate is Googles Keyword Planner?

[Sika22]

I did some keyword research for our company.  Some of the terms we got 100,000 search volume for in 2011 now have only 90 monthly searches.  I am doing exact match for both US and Global and neither are any where near those high of numbers.  Now I can't say how the old report on this was done but we are all a little skeptical of these numbers.  Is there any other tool out there for search volume on Google?  The Moz tool while it lists Google as an option only does Bing.  Thank you!

[DonnaDuncan]

Given you "can't say" how the old numbers were derived, you might try plugging your key phrases into Google trends to see if there's been an obvious diminishing of search volume over the past few years. That might help you figure out whether there's been less searches or whether your "old" numbers are from exact match searches or something else.