After Google released its Q3 2011 earnings yesterday, I saw some people making odd comparisons between Facebook and Google+. A few journalists and analysts started pointing out that Facebook is now 20 times the size of Google+, or put another way, that Google+ already has 5 percent of Facebook's user base. This is simply not true.
On July 14, 2011, during the company's Q2 2011 earnings call, Google announced Google+ had hit 10 million users. On October 13, 2011, during its Q3 2011 earnings call, the search giant revealed its social network now has over 40 million users. In other words, Google+ saw 30 million new users join in the three months, or an average of 10 million users per month.
On July 6, 2011, during the company's video calling announcement, Facebook announced it had passed 750 million active users. On September 22, during its 2011 f8 developer conference, the social networking giant revealed it now has over 800 million active users. In other words, Facebook saw 50 million new members use its service in 10 weeks, or an average of 20 million newly active users per month.
I purposefully worded the above two paragraphs differently. If you didn't notice, I'll underline the discrepancy for you: Google is counting the number of users that have joined Google+. Facebook counts the number of users who log in to the service at least once within the last 30 days.
These are two completely different metrics and they thus cannot be compared directly. Some people just tend to forget – or purposefully omit – this fact. It's fairly obvious that Facebook's number of sign ups is much bigger than 800 million while the number of active users on Google+ is much lower than 40 million.
Any online service, including social networks, have users sign up and never come back. Facebook has thus seen more than 800 million users sign up so far. At the same time, not all of the 40 million users that signed up for Google+ are still active.