Why does opensiteexplorer tell me I have 292 linking domains and google webmasteer tools says 528?

[eric_since1910.com]

Does anyone have any idea why opensiteexplorer has a specific number of linking domains while google webmaster tools say another?

I understand opensiteexplorer needs to update itself, but I have seen this discrepancy for months!

Any ideas?

[HiveDigitalInc]

Google Webmaster Tools and Open Site Explorer rely on different data. SEOMoz has their own index of the web which they use to create the link statistics you see in Open Site Explorer. Their index is substantially smaller than Google's, but represents a significant proportion of the overall web.

What really matters is proportion, though. How many root domains do you have linking vs. your competitors? You can't get that information from Google Webmaster Tools, but you can from OSE.