The question of how Facebook decides how many people see the content that you post has been a pretty volatile topic over the last few months. Basically, Facebook has been accused to limiting the reach of people and page’s normal posts in order to force them into using Promoted Posts, thus generating revenue for Facebook. Facebook adamantly denies all of this. But more on that later.

In the aforementioned climate, just days after they released a long defense of their ranking algorithms and practices, Facebook has published a new study on “estimating audience size” on the site.

Spolier alert: Facebook says that people vastly underestimate how many people see their posts.

Facebook asked 1,131 users a simple question: How many of your friends do you think actually saw this (a single, specific) post?

Here are the results:

“By and large, people underestimated the size of their audience. When we asked users how many friends saw a particular post, the median user guessed 20 friends, while the actual median was 78.”

For the more visually oriented, Facebook has provided some graphical support. Every dot under the dotted line represents a user who underestimated the reach of their post:

Overall, Facebook says that the median user reaches 60% of their friends over the course of a month.

Facebook expanded their research and looked at 220,000 users and the connection between audience (how many saw the post) and both total number of friends and number of comments on the post. Spoiler alert: things vary quite a bit and neither is a very good predictor of eventual reach of any given post.

What the data does do is show that as you gain more friends, the percentage of them who will see your posts decreases. But, the high end of the audience reach is probably a bit higher than you thought.

Facebook has said in the past that overall, any post will be seen by somewhere around 16% of a user’s friends. This new data shows that the variations are pretty wild. For instance, a person with 400 friends can possibly have a reach of just a couple of percent, all the way up to nearly 40%.

Of course, plenty of things go into who sees your posts on Facebook. For instance: number of friends, what time of day you post it, how many shares it gets, competition in friends’ news feeds and yes, Facebook’s system of ranking algorithms that determine much of this.

After once again being accused of decreasing the visibility of users’ posts in order to promote their Promoted Posts product, Facebook defended themselves earlier this week.

“There have been recent claims suggesting that our News Feed algorithm suppresses organic distribution of posts in favor of paid posts in order to increase our revenue. This is not true,” they said.

Still, page owners continue to report that they are seeing less reach on their posts than they used to, and many blame Facebook for shady practices.

This new research from Facebook suggests that people have a tendency to underestimate the reach of their posts, and that using likes and comments on a post to judge how many people actually saw it is unreliable at best.

What an interesting time to publish such a message. Coincidence? I think not.