AdWords Keyword Tools Are Not Always Correct!

I'm sure by now that everyone who reads here knows the AdWords Keyword Tool is showing numbers instead of the graphs it would show just a few weeks back. I think one of the big questions on everyone's mind is just how accurate is the data being shown? I decided to take a look in a few accounts I have access to and found at least keyword that seems to meet all the criteria I would use for a test. I found one in particular that was live in November, and the AdWords Keyword Tool does reference November data.

Here are a few details:

- The keyword is exact match.
- 100% impression share for November.
- It's opted in Google + Search Network
- US targeting

When logged into the account the keyword tool indicates that the approximate November search volume was 44,830. That estimate is based on exact match and the correct location targeting. Here's what surprised me - the actual number of impressions that keyword received in November was 56,770. Do a little rounding and the estimate provided by the keyword tool comes out within 10% of the real number.

Now of course that's one keyword in one account and in no way am I trying to imply that the keyword tool will be that accurate in all cases. I'm honestly surprised though at just how accurate it is in this case.

Anyone else seeing similar numbers?