14 DAY TRIAL // Google+ has continued to grow since launch. It started out great and quickly gained 10 million users. But, despite not being available to all users, the hype around the project meant that growth was easy to achieve in the first weeks.
Things slowed down after a while, but then Google+ user numbers jumped 30 percent in just a couple of days last week.
Of course, Google+ was opened up to the public last week, which would account for part of the boost, but what probably mattered most was the fact that it was advertised and featured on the Google homepage, one of the most trafficked pages on the web.
Regardless of the reason, Google's move may have pushed Google+ numbers by almost 10 million, reaching an estimated 43.4 million users.
The numbers come from Ancestry.com founder Paul Allen, who has been keeping track of Google+ user numbers via his 'uncommon surname' method.
"On September 9, our model showed 28.7 million users. This morning, our model shows 37.8 million users, with most of the growth coming in the last 2 days," Paul Allen wrote on Google+.
"By adding a fudge factor (see below) to account for private user profiles and for non-Roman surnames (both of which are totally overlooked by our surname counting model), my current estimate is 43.4 million users," he said.
He tracks 400 uncommon surnames in the US and checks to see how many of those are used on Google+. He then correlates the numbers with US census data to come up with an estimate of the total Google+ population.
There are several caveats to the model, but it has proven remarkably accurate before, when it predicted that Google+ had 10 million users before Google revealed the number itself.
While absolute numbers may not be entirely accurate, it is very possible that, at this time, Google+ has close to 50 million users worldwide. How many of those are active users, though, is another issue.