GWT data v SEO Moz data

[MrPaulB]

I'm sure there's a simple explanation but I can't find it -

Looking through the GWT avg position data v SEOMoz ranking data and Market Samurai data there is a large discrepancy. For one term that we hold #1, and have held for a month or two GWTis showing that the avg position is 180 (and down 30).

Any reason you know of why the GWT avg position data would be so out of whack with our SERP's and other data?

Thanks.

[KeriMorgret]

I can't find the reference right now, but I believe I've seen something about if you have a second page at a lower position that's also ranking for that keyword it can throw off the average position. GWT position data always seems way lower than reality for me as well.