Sep. 18, 2012 at 12:57 PM ET
Google says its one-year-old social network now has more than 100 million monthly active users, but if you think you remember hearing a higher number recently, you're right.
The search giant said at its Google I/O developers conference in June that it had 150 million users who sign on once or more a month.
Vic Gundotra, Google's senior vice president, engineering, said on his own Google+ page Monday that "I’m happy to report that we have just crossed 100,000,000 monthly active users on Google+ (plus.google.com and mobile app)."
Gundotra prefaced that stat by saying that this week the company "hit an important milestone — over 400,000,000 people have upgraded to Google+. It was only a year ago that we opened public sign-up, and we couldn’t have imagined that so many people would join in just 12 months."
All well and good, but what accounts for the discrepancy in the monthly active user figures?
A Google spokesman told NBC News it's not that the company has changed its numbers. Rather, he said, there are two different ways monthly active users are measured.
Google+ has 100 million monthly active users when Google+ itself is measured as a destination on the Web or mobile by users.
But, when Google+ is viewed as a "social layer" — which some say it should be described as, versus a social network — it has 150 million monthly active users. What's a social layer? It might include those who used Google+ circles or Android users "who plus oned an app," Gundotra said in explaining the difference.
In other words, the Google spokesman told NBC News, "You're engaging with a feature of Google+, as a G+ user, but not necessarily in plus.google.com," the Google+ site.
Numbers game? Perhaps. Still, Google+ faces a battle in a crowded social media world. As one fan, Kyle Beatty, noted in comments under Gundotra's posting, "400,000,000 people and only two of my friends are using it ... sparingly. I love the platform, but I can't get any of my family and friends to use it. Any suggestions?"