Paul Allen, a Google+ watcher, says the network will hit 100.8 million users by Wednesday, Feb 1 evening. Google’s most recent figure for Google+ was 90 million, which Larry Page announced on Jan. 19.

In a blog post, Allen noted that the network has grown more than 10% in that two-week period.

Allen, the founder of Ancestry.com, takes an unusual approach to come by his estimates: He and his staff run hundreds of queries on surnames they’ve been tracking since July and then extrapolate the size of the network. His method seems to work: Allen’s numbers are often very close to figures that Google cites a few days later.

Allen has also predicted that Google+ will hit 400 million users by year’s end. That’s half the number that Facebook currently claims, Mashable reports.