Last week we had a lot of attention over Google saying 20 to 25% of queries are new. Well, it turns out that the figure is not an exact figure. Google now said it is a ballpark figure, as quoted on Google Blogoscoped:
First, I want to clarify that we do not keep searches from 1998. The 20-25% we’ve stated is only an estimate, which is why we gave it a wide range. We cannot compute the exact number, so we gave a ballpark number, based on some reasonable assumptions.
Postscript: Matt Cutts just added a comment at Google Blogoscoped saying:
Philipp, I think that’s a pretty accurate estimate if you look over a time period of a month or so. So if you had queries from the last month or so, 20-25% of queries the next day would be new/unique. It also depends a little bit about whether you’re defining it only as web queries, or all queries to Google (e.g. blog search, book search, patent search, etc.).