From the website: How do we calculate the number of Google+ accounts? Before November 15, 2012, we use the numbers Google provided publicly. Since then, we be

From the website: How do we calculate the number of Google+ accounts? Before November 15, 2012, we use the numbers Google provided publicly. Since then, we began calculating the number on our own. To do this, we first download the Google+ Sitemap. Then, we walk through this file and find all the sub-sitemaps available. For each sub-sitemap we find, we download it and then count the number of Google+ profiles and the number of Google profiles contained within it. Tallying all this gives us two numbers: Google+ users and Google users. We do this once a day. However, the Google+ sitemap has been known to go down (404) periodically. It was missing completely for almost two months from mid April 2013 until mid June 2013. As such, you may see a sparsity of data points during such time frames. How do you count the size of the index? This is a much simpler process. We simply perform a specific Google search across Google+ and a slightly different Google search across Google+. We then take the largest number of results returned from these two searches giving us our Google+ index size. From the author on G+: It's also entirely likely that a large percentage of the number I am reporting here are G+ profiles created by users activating new Android devices and never using the account for any activity https://plus.google.com/112767041460502214504/posts/SjWJLWeZ6tJ https://plus.google.com/112767041460502214504/posts/SjWJLWeZ...