When you make a post on Facebook, have you ever wondered how many of your friends see it? While we’d all like to think our friends are panting to see our earth-shattering posts, the truth is, some people don’t log in everyday, others go on vacation and some don’t read any posts except the most eye-catching ones.

If you use Facebook for your business, you may wonder how many of your customers are regularly encountering your posts. After all, it’s hard to understand whether customers are seeing posts and simply not responding (which may mean you need to make your posts a bit more compelling), or missing posts entirely (which may mean you need to make yourself a bit more visible). 

Facebook recently did a little analysis in conjunction with Stanford University. The social media company analyzed audience logs from 222,000 Facebook users’ posts over the course of one month, and determined that each post is typically seen by one third of a user’s friends, and that these users generally reach about 61 percent of their friends each month.

The interesting part is that researchers asked Facebook users how many of their friends they would estimate saw each post, and the average guess was 27 percent, which means that users consistently underestimate how many people see their posts. (Remember, just because nobody “liked” it didn’t mean nobody saw it.)

The research was carried out by a Stanford University computer scientist, Michael S. Bernstein, and three members of the Facebook’s data science team — Eytan Bakshy, Moira Burke and Brian Karrer. The results of the study will be presented at an academic conference next month, the New York Times is reporting today.