Today at the Strata Summit on Big Data, Google’s Bradley Horowitz noted an intriguing statistic about Google Plus usage: users of Google Plus are two to three times as likely to post content to private circles than they are to post it publicly. As our own Marshall Kirkpatrick commented, these numbers suggest the Circles metaphor is working.

Horowitz is VP of Product Management and a leader of the Google Plus social network, so he knows better than anyone the usage data. Still, I am very surprised to hear that private posts are 2-3 times as likely as public posts on Google Plus. I myself hardly ever post privately and I had thought that not many of the people I follow do either. So let’s do an informal poll: do you regularly post privately in Google Plus?

I also asked the question on my own Google Plus profile, where you can leave a comment if you like.

This statistic from Horowitz may explain the recently reported apparent drop in Google Plus activity. If 2-3 times more people are posting privately than publicly, then it’s likely that Google Plus usage is being significantly under-reported. However we’d love to see actual numbers from Google about this, so we will follow up with Horowitz.

We’ll evaluate the replies to our informal poll in a later post.